SEC Info℠  
    Home      Search      My Interests      Help      Sign In      Please Sign In

Altair Engineering Inc. – ‘10-Q’ for 9/30/23 – ‘EX-101.LAB’

On:  Thursday, 11/2/23, at 4:30pm ET   ·   For:  9/30/23   ·   Accession #:  950170-23-58280   ·   File #:  1-38263

Previous ‘10-Q’:  ‘10-Q’ on 8/3/23 for 6/30/23   ·   Next & Latest:  ‘10-Q’ on 5/2/24 for 3/31/24   ·   1 Reference:  By:  Altair Engineering Inc. – ‘10-K’ on 2/22/24 for 12/31/23

Find Words in Filings emoji
 		  in    Show  and   ↓Hints

  As Of               Filer                 Filing    For·On·As Docs:Size             Issuer                      Filing Agent

11/02/23  Altair Engineering Inc.           10-Q        9/30/23   79:12M                                    Donnelley … Solutions/FA

Quarterly Report   —   Form 10-Q

Filing Table of Contents

Document/Exhibit                   Description                      Pages   Size 

 1: 10-Q        Quarterly Report                                    HTML   4.16M 
 2: EX-10.1     Material Contract                                   HTML    124K 
 3: EX-31.1     Certification -- §302 - SOA'02                      HTML     27K 
 4: EX-31.2     Certification -- §302 - SOA'02                      HTML     27K 
 5: EX-32.1     Certification -- §906 - SOA'02                      HTML     25K 
11: R1          Document and Entity Information                     HTML     79K 
12: R2          Consolidated Balance Sheets                         HTML    138K 
13: R3          Consolidated Balance Sheets (Parenthetical)         HTML     46K 
14: R4          Consolidated Statements of Operations (Unaudited)   HTML    120K 
15: R5          Consolidated Statements of Comprehensive Income     HTML     51K 
                (Unaudited)                                                      
16: R6          Consolidated Statements of Comprehensive Income     HTML     29K 
                (Unaudited) (Parenthetical)                                      
17: R7          Consolidated Statements of Changes in               HTML    129K 
                Stockholders' Equity (Unaudited)                                 
18: R8          Consolidated Statements of Cash Flows (Unaudited)   HTML    122K 
19: R9          Pay vs Performance Disclosure                       HTML     36K 
20: R10         Insider Trading Arrangements                        HTML     29K 
21: R11         Organization and Description of Business            HTML     84K 
22: R12         Recent Accounting Guidance                          HTML     36K 
23: R13         Revenue from Contracts with Customers               HTML     95K 
24: R14         Supplementary Information                           HTML    181K 
25: R15         Goodwill and Other Intangible Assets                HTML    133K 
26: R16         Debt                                                HTML    104K 
27: R17         Fair Value Measurements                             HTML     32K 
28: R18         Stock-Based Compensation                            HTML    129K 
29: R19         Net Income Per Share                                HTML    118K 
30: R20         Income Taxes                                        HTML     51K 
31: R21         Accumulated Other Comprehensive Loss                HTML     61K 
32: R22         Commitments and Contingencies                       HTML     30K 
33: R23         Segment Information                                 HTML    187K 
34: R24         Organization and Description of Business            HTML     93K 
                (Policies)                                                       
35: R25         Organization and Description of Business            HTML     76K 
                (Policies) (Tables)                                              
36: R26         Revenue from Contracts with Customers (Tables)      HTML     81K 
37: R27         Supplementary Information (Tables)                  HTML    178K 
38: R28         Goodwill and Other Intangible Assets (Tables)       HTML    135K 
39: R29         Debt (Tables)                                       HTML     81K 
40: R30         Stock-Based Compensation (Tables)                   HTML    122K 
41: R31         Net (Loss) Income Per Share (Tables)                HTML    118K 
42: R32         Income Taxes (Tables)                               HTML     46K 
43: R33         Accumulated Other Comprehensive Loss (Tables)       HTML     60K 
44: R34         Segment Information (Tables)                        HTML    184K 
45: R35         Organization and Description of Business            HTML     44K 
                (Policies) - Schedule of Changes Made to the                     
                Consolidated Statement Of Income (Details)                       
46: R36         Revenue from Contracts with Customers - Schedule    HTML     47K 
                of Disaggregation of Revenue (Detail)                            
47: R37         Revenue from Contracts with Customers - Additional  HTML     55K 
                Information (Detail)                                             
48: R38         Revenue from Contracts with Customers - Additional  HTML     26K 
                Information (Detail)1                                            
49: R39         Supplementary Information - Reconciliation of       HTML     32K 
                Cash, Cash Equivalents and Restricted Cash                       
                (Detail)                                                         
50: R40         Supplementary Information - Summary of Property     HTML     45K 
                and Equipment (Detail)                                           
51: R41         Supplementary Information - Additional Information  HTML     43K 
                (Detail)                                                         
52: R42         Supplementary Information - Summary of Other        HTML     49K 
                Accrued Expenses and Current Liabilities (Detail)                
53: R43         Supplementary Information - Summary of Other        HTML     33K 
                Long-term Liabilities (Detail)                                   
54: R44         Supplementary Information - Schedule of Other       HTML     32K 
                (Income) Expense, Net (Detail)                                   
55: R45         Goodwill and Other Intangible Assets - Changes in   HTML     31K 
                Carrying Amount of Goodwill Attributable to                      
                Software Reportable Segment (Detail)                             
56: R46         Goodwill and Other Intangible Assets - Schedule of  HTML     58K 
                Other Intangible Assets (Detail)                                 
57: R47         Goodwill and Other Intangible Assets - Additional   HTML     26K 
                Information (Detail)                                             
58: R48         Debt - Additional Information (Detail)              HTML    109K 
59: R49         Debt - Schedule of Convertible Notes (Detail)       HTML     43K 
60: R50         Debt - Schedule of Interest Expense Recognized      HTML     42K 
                Related to Convertible Notes (Detail)                            
61: R51         Fair Value Measurements - Additional Information    HTML     28K 
                (Detail)                                                         
62: R52         Stock-based Compensation - Additional Information   HTML     76K 
                (Detail)                                                         
63: R53         Stock-based Compensation - Summary of Restricted    HTML     35K 
                Stock Units Awarded (Detail)                                     
64: R54         Stock-based Compensation - Summary of Stock Option  HTML     64K 
                Activity under 2017 Plan (Detail)                                
65: R55         Stock-based Compensation - Summary of Stock-Based   HTML     35K 
                Compensation Expense (Detail)                                    
66: R56         Net (Loss) Income Per Share - Computation of        HTML     65K 
                Numerators and Denominators Used in Basic and                    
                Diluted Net (Loss) Income Per Share Amounts                      
                (Detail)                                                         
67: R57         Net (loss) income per share - Schedule of           HTML     32K 
                Anti-dilutive Shares Excluded from Computation of                
                Diluted Net Loss Per Share (Detail)                              
68: R58         Income Taxes - Schedule of Income Tax Expense and   HTML     29K 
                Effective Tax Rate (Detail)                                      
69: R59         Income Taxes - Additional Information (Detail)      HTML     24K 
70: R60         Accumulated Other Comprehensive Loss - Components   HTML     61K 
                of Accumulated Other Comprehensive Loss (Detail)                 
71: R61         Segment Information - Additional Information        HTML     24K 
                (Detail)                                                         
72: R62         Segment Information - Schedule of Segment           HTML     39K 
                Reporting Information (Detail)                                   
73: R63         Segment Information - Reconciliation of U.S. GAAP   HTML     46K 
                Loss Before Income Taxes to Adjusted EBITDA                      
                (Detail)                                                         
74: R64         Segment Information - Reconciliation of U.S. GAAP   HTML     39K 
                Income (Loss) Before Income Taxes to Adjusted                    
                EBITDA (Parenthetical) (Detail)                                  
77: XML         IDEA XML File -- Filing Summary                      XML    145K 
75: XML         XBRL Instance -- altr-20230930_htm                   XML   2.90M 
76: EXCEL       IDEA Workbook of Financial Report Info              XLSX    131K 
 9: EX-101.CAL  XBRL Calculations -- altr-20230930_cal               XML    181K 
 7: EX-101.DEF  XBRL Definitions -- altr-20230930_def                XML    731K 
10: EX-101.LAB  XBRL Labels -- altr-20230930_lab                     XML   1.25M 
 6: EX-101.PRE  XBRL Presentations -- altr-20230930_pre              XML    982K 
 8: EX-101.SCH  XBRL Schema -- altr-20230930                         XSD    171K 
78: JSON        XBRL Instance as JSON Data -- MetaLinks              533±   815K 
79: ZIP         XBRL Zipped Folder -- 0000950170-23-058280-xbrl      Zip    379K

‘EX-101.LAB’   —   XBRL Labels — altr-20230930_lab

This Exhibit is an XBRL File.

                                                                                                                                                                                
<?xml version="1.0" encoding="windows-1252"?>
<!-- DFIN New ActiveDisclosure (SM) XBRL Linkbase Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date :2023-11-01T16:03:44.6963+00:00 -->
<!-- Copyright (c) 2023 Donnelly Financial Solutions, Inc. All Rights Reserved. -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedLabel" xlink:type="simple"/>
<link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTerseLabel" xlink:type="simple"/>
<link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedTotalLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTotalLabel" xlink:type="simple"/>
<link:labelLink xlink:role="http://www.xbrl.org/2003/role/link" xlink:title="labelLink" xlink:type="extended">
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentTransitionReport" xlink:label="dei_DocumentTransitionReport"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligation" xlink:label="us-gaap_RevenueRemainingPerformanceObligation"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestOnConvertibleDebtNetOfTax" xlink:label="us-gaap_InterestOnConvertibleDebtNetOfTax"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_GoodwillAffectOfForeignCurrencyTranslationGainLossAndOther" xlink:label="altr_GoodwillAffectOfForeignCurrencyTranslationGainLossAndOther"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="us-gaap_OtherLiabilitiesNoncurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="us-gaap_RestrictedStockUnitsRSUMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_AccruedObligationsForAcquisitionOfBusinesses" xlink:label="altr_AccruedObligationsForAcquisitionOfBusinesses"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SoftwareRelatedServiceMember" xlink:label="altr_SoftwareRelatedServiceMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresTextBlock" xlink:label="us-gaap_FairValueDisclosuresTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_AccountsReceivableNetCurrentMember" xlink:label="altr_AccountsReceivableNetCurrentMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ComputerEquipmentAndSoftwareMember" xlink:label="altr_ComputerEquipmentAndSoftwareMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueTableTextBlock" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" xlink:label="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="us-gaap_ConcentrationRiskByTypeAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityCurrent" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock" xlink:label="us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_PaymentsForRepurchaseOfCommonStockShares" xlink:label="altr_PaymentsForRepurchaseOfCommonStockShares"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepositLiabilitiesAccruedInterest" xlink:label="us-gaap_DepositLiabilitiesAccruedInterest"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConvertibleDebtFairValueDisclosures" xlink:label="us-gaap_ConvertibleDebtFairValueDisclosures"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GoodwillAcquiredDuringPeriod" xlink:label="us-gaap_GoodwillAcquiredDuringPeriod"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TemporaryEquitySharesIssued" xlink:label="us-gaap_TemporaryEquitySharesIssued"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncashOrPartNoncashAcquisitionsLineItems" xlink:label="us-gaap_NoncashOrPartNoncashAcquisitionsLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_TwoThousandTwentyThreeAcquisitionsMember" xlink:label="altr_TwoThousandTwentyThreeAcquisitionsMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="us-gaap_BalanceSheetLocationAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsCurrent" xlink:label="us-gaap_AssetsCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressStateOrProvince" xlink:label="dei_EntityAddressStateOrProvince"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_LitigationCaseTypeDomain" xlink:label="srt_LitigationCaseTypeDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxAssetsNet" xlink:label="us-gaap_DeferredIncomeTaxAssetsNet"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_TermLicensesAndOtherMember" xlink:label="altr_TermLicensesAndOtherMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_StockIssuedDuringPeriodSharesPrivatePlacementNewIssues" xlink:label="altr_StockIssuedDuringPeriodSharesPrivatePlacementNewIssues"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_TradingSymbol" xlink:label="dei_TradingSymbol"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock" xlink:label="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock" xlink:label="us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_DocumentAndEntityInformationTable" xlink:label="altr_DocumentAndEntityInformationTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAbstract" xlink:label="us-gaap_NetIncomeLossAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingAndMarketingExpenseMember" xlink:label="us-gaap_SellingAndMarketingExpenseMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding" xlink:label="us-gaap_SharesOutstanding"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationDisclosureTextBlock" xlink:label="us-gaap_BusinessCombinationDisclosureTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressCityOrTown" xlink:label="dei_EntityAddressCityOrTown"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesTwoMember" xlink:label="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesTwoMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_StockRepurchaseProgramAveragePricePerShare" xlink:label="altr_StockRepurchaseProgramAveragePricePerShare"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureTextBlock" xlink:label="us-gaap_DebtDisclosureTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_RightOfUseAssetsUnderFinanceLeasesMember" xlink:label="altr_RightOfUseAssetsUnderFinanceLeasesMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="us-gaap_LiabilitiesCurrentAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="us-gaap_AssetsCurrentAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax" xlink:label="us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfStockholdersEquityAbstract" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseLiabilityCurrent" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentMaturityDate" xlink:label="us-gaap_DebtInstrumentMaturityDate"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="us-gaap_PropertyPlantAndEquipmentNet"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_PromissoryNotesIssuedAndDeferredPaymentObligationsForAcquisitions" xlink:label="altr_PromissoryNotesIssuedAndDeferredPaymentObligationsForAcquisitions"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestructuringCharges" xlink:label="us-gaap_RestructuringCharges"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_PaymentForRepurchaseOfCommonStockShares" xlink:label="altr_PaymentForRepurchaseOfCommonStockShares"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability" xlink:label="us-gaap_BusinessCombinationContingentConsiderationLiability"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract" xlink:label="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCentralIndexKey" xlink:label="dei_EntityCentralIndexKey"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherIntangibleAssetsMember" xlink:label="us-gaap_OtherIntangibleAssetsMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameDomain" xlink:label="us-gaap_PlanNameDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilitiesDisclosureAbstract" xlink:label="us-gaap_OtherLiabilitiesDisclosureAbstract"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_TwoThousandAndSeventeenEquityIncentivePlanMember" xlink:label="altr_TwoThousandAndSeventeenEquityIncentivePlanMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesCommissionsAndFees" xlink:label="us-gaap_SalesCommissionsAndFees"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="us-gaap_PreferredStockSharesOutstanding"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfGoodwillTextBlock" xlink:label="us-gaap_ScheduleOfGoodwillTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesCurrent" xlink:label="us-gaap_LiabilitiesCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityTaxIdentificationNumber" xlink:label="dei_EntityTaxIdentificationNumber"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfDebtIssuanceCosts" xlink:label="us-gaap_PaymentsOfDebtIssuanceCosts"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ConceptEngineeringMember" xlink:label="altr_ConceptEngineeringMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ProfessionalSoftwareServicesMember" xlink:label="altr_ProfessionalSoftwareServicesMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourAndTwoThousandTwentySevenMember" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourAndTwoThousandTwentySevenMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PlanNameAxis" xlink:label="us-gaap_PlanNameAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_RevenueFromContractsWithCustomersLineItems" xlink:label="altr_RevenueFromContractsWithCustomersLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassAMember" xlink:label="us-gaap_CommonClassAMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityRegistrantName" xlink:label="dei_EntityRegistrantName"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet" xlink:label="us-gaap_DeferredFinanceCostsNet"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SoftwareMember" xlink:label="altr_SoftwareMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SupplementalCashFlowInformationAbstract" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_NumberOfPriorBusinessAcquistionsValuationFinalized" xlink:label="altr_NumberOfPriorBusinessAcquistionsValuationFinalized"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet" xlink:label="us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromStockOptionsExercised" xlink:label="us-gaap_ProceedsFromStockOptionsExercised"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SignificantAccountingPoliciesTextBlock" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedIncomeTaxesCurrent" xlink:label="us-gaap_AccruedIncomeTaxesCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="us-gaap_StatementBusinessSegmentsAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConversionOfStockSharesConverted1" xlink:label="us-gaap_ConversionOfStockSharesConverted1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LandMember" xlink:label="us-gaap_LandMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonstock" xlink:label="altr_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonstock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:label="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_FurnitureEquipmentAndOtherMember" xlink:label="altr_FurnitureEquipmentAndOtherMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="us-gaap_DebtDisclosureAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BuildingAndBuildingImprovementsMember" xlink:label="us-gaap_BuildingAndBuildingImprovementsMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_AmountWithheldOnBehalfOfEmployeesForFuturePurchase" xlink:label="altr_AmountWithheldOnBehalfOfEmployeesForFuturePurchase"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCurrentReportingStatus" xlink:label="dei_EntityCurrentReportingStatus"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities" xlink:label="us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="us-gaap_CommonStockSharesAuthorized"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PutOptionMember" xlink:label="us-gaap_PutOptionMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_TwoThousandAndTwentyOneEmployeeStockPurchasePlanMember" xlink:label="altr_TwoThousandAndTwentyOneEmployeeStockPurchasePlanMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="us-gaap_ResearchAndDevelopmentExpense"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTable"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_RevenueFromContractsWithCustomersTable" xlink:label="altr_RevenueFromContractsWithCustomersTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:label="us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="us-gaap_AmortizationOfIntangibleAssets"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNoncashIncomeExpense" xlink:label="us-gaap_OtherNoncashIncomeExpense"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ConvertibleSeniorNotesDueInTwoThousandTwentySevenMember" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentySevenMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CurrentFiscalYearEndDate" xlink:label="dei_CurrentFiscalYearEndDate"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensation" xlink:label="us-gaap_ShareBasedCompensation"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_StockPurchaseProgramSharesAcquired" xlink:label="altr_StockPurchaseProgramSharesAcquired"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingIncomeLoss" xlink:label="us-gaap_OperatingIncomeLoss"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued" xlink:label="us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="us-gaap_IncomeTaxExpenseBenefit"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConvertibleLongTermNotesPayable" xlink:label="us-gaap_ConvertibleLongTermNotesPayable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NatureOfOperations" xlink:label="us-gaap_NatureOfOperations"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions" xlink:label="us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="us-gaap_ConcentrationRiskPercentage1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ProceedsFromEmployeeStockPurchasePlanContributions" xlink:label="altr_ProceedsFromEmployeeStockPurchasePlanContributions"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="us-gaap_DisaggregationOfRevenueTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLossAttributableToParentDiluted" xlink:label="us-gaap_NetIncomeLossAttributableToParentDiluted"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxesPaid" xlink:label="us-gaap_IncomeTaxesPaid"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerTextBlock" xlink:label="us-gaap_RevenueFromContractWithCustomerTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:label="us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LicenseMember" xlink:label="us-gaap_LicenseMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToInitialPurchaser" xlink:label="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToInitialPurchaser"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_LineOfCreditFacilityIncreaseInBorrowingCapacity" xlink:label="altr_LineOfCreditFacilityIncreaseInBorrowingCapacity"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="us-gaap_OperatingExpensesAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentAbstract" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SettlementOfConvertibleSeniorNotes" xlink:label="altr_SettlementOfConvertibleSeniorNotes"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_FairValueExpenseRecognized" xlink:label="altr_FairValueExpenseRecognized"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="us-gaap_OtherAssetsNoncurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleIfConvertedValueInExcessOfPrincipal" xlink:label="us-gaap_DebtInstrumentConvertibleIfConvertedValueInExcessOfPrincipal"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Depreciation" xlink:label="us-gaap_Depreciation"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestPaidNet" xlink:label="us-gaap_InterestPaidNet"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonClassBMember" xlink:label="us-gaap_CommonClassBMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_DebtInstrumentConvertibleThresholdBusinessDays" xlink:label="altr_DebtInstrumentConvertibleThresholdBusinessDays"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="us-gaap_StockholdersEquityAbstract"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_DocumentAndEntityInformationLineItems" xlink:label="altr_DocumentAndEntityInformationLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DevelopedTechnologyRightsMember" xlink:label="us-gaap_DevelopedTechnologyRightsMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage" xlink:label="us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfGoodsAndServicesSold" xlink:label="us-gaap_CostOfGoodsAndServicesSold"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization" xlink:label="altr_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ScheduleOfOtherIntangibleAssetsTableTextBlock" xlink:label="altr_ScheduleOfOtherIntangibleAssetsTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareAbstract" xlink:label="us-gaap_EarningsPerShareAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ExpenseOnRepurchaseOfConvertibleSeniorNote" xlink:label="altr_ExpenseOnRepurchaseOfConvertibleSeniorNote"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesTable" xlink:label="us-gaap_LossContingenciesTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_LitigationCaseAxis" xlink:label="srt_LitigationCaseAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentDomain" xlink:label="us-gaap_SegmentDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LicenseAndServiceMember" xlink:label="us-gaap_LicenseAndServiceMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNoncurrentAssetsMember" xlink:label="us-gaap_OtherNoncurrentAssetsMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SoftwareSegmentMember" xlink:label="altr_SoftwareSegmentMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic" xlink:label="us-gaap_EarningsPerShareBasic"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ConvertibleSharesMember" xlink:label="altr_ConvertibleSharesMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock" xlink:label="us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="us-gaap_CommitmentsAndContingencies"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementAbstract" xlink:label="us-gaap_IncomeStatementAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostNetCurrent" xlink:label="us-gaap_CapitalizedContractCostNetCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesLineItems" xlink:label="us-gaap_LossContingenciesLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentPeriodEndDate" xlink:label="dei_DocumentPeriodEndDate"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionNameDomain" xlink:label="us-gaap_DebtConversionNameDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="us-gaap_EarningsPerShareDiluted"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductsAndServicesDomain" xlink:label="srt_ProductsAndServicesDomain"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_CurrencyGainsOnAcquisitionRelatedIntercompanyLoans" xlink:label="altr_CurrencyGainsOnAcquisitionRelatedIntercompanyLoans"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CostOfSalesMember" xlink:label="us-gaap_CostOfSalesMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueFromContractWithCustomerAbstract" xlink:label="us-gaap_RevenueFromContractWithCustomerAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SupplementaryInformationTextBlock" xlink:label="altr_SupplementaryInformationTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_StockIssuedDuringPeriodValuePrivatePlacementNewIssues" xlink:label="altr_StockIssuedDuringPeriodValuePrivatePlacementNewIssues"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentDescription" xlink:label="us-gaap_DebtInstrumentDescription"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NumberOfReportableSegments" xlink:label="us-gaap_NumberOfReportableSegments"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember" xlink:label="us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesAndExciseTaxPayableCurrentAndNoncurrent" xlink:label="us-gaap_SalesAndExciseTaxPayableCurrentAndNoncurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossBeforeTax" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock" xlink:label="us-gaap_PaymentsForRepurchaseOfCommonStock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent" xlink:label="us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_NumberOfEqualVestingInstallments" xlink:label="altr_NumberOfEqualVestingInstallments"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_LossOnMarkToMarketAdjustmentOfContingentConsideration" xlink:label="altr_LossOnMarkToMarketAdjustmentOfContingentConsideration"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LicenseAndMaintenanceMember" xlink:label="us-gaap_LicenseAndMaintenanceMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNoncurrentLiabilitiesTableTextBlock" xlink:label="us-gaap_OtherNoncurrentLiabilitiesTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions" xlink:label="us-gaap_StockIssuedDuringPeriodValueAcquisitions"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressPostalZipCode" xlink:label="dei_EntityAddressPostalZipCode"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityInteractiveDataCurrent" xlink:label="dei_EntityInteractiveDataCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingAndMarketingExpense" xlink:label="us-gaap_SellingAndMarketingExpense"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_TwoThousandTwentyOneAcquisitionsMember" xlink:label="altr_TwoThousandTwentyOneAcquisitionsMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GranteeStatusDomain" xlink:label="us-gaap_GranteeStatusDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsPayable" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementAdjustmentMember" xlink:label="srt_RestatementAdjustmentMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityAbstract" xlink:label="us-gaap_EquityAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShortTermDebtTable" xlink:label="us-gaap_ScheduleOfShortTermDebtTable"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_TheTimingOfPayrollDeductionsMember" xlink:label="altr_TheTimingOfPayrollDeductionsMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementAxis" xlink:label="srt_RestatementAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityIncorporationStateCountryCode" xlink:label="dei_EntityIncorporationStateCountryCode"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent" xlink:label="us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AllOtherSegmentsMember" xlink:label="us-gaap_AllOtherSegmentsMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_DebtInstrumentConvertibleThresholdMaximumPercentageOfProductOfLastReportedSalePriceOfCommonStock" xlink:label="altr_DebtInstrumentConvertibleThresholdMaximumPercentageOfProductOfLastReportedSalePriceOfCommonStock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" xlink:label="us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LocalPhoneNumber" xlink:label="dei_LocalPhoneNumber"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures" xlink:label="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Goodwill" xlink:label="us-gaap_Goodwill"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfNotesPayable" xlink:label="us-gaap_RepaymentsOfNotesPayable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfCashFlowsAbstract" xlink:label="us-gaap_StatementOfCashFlowsAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TemporaryEquityRedemptionPricePerShare" xlink:label="us-gaap_TemporaryEquityRedemptionPricePerShare"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="us-gaap_SegmentReportingInformationLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GrossProfit" xlink:label="us-gaap_GrossProfit"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedTranslationAdjustmentMember" xlink:label="us-gaap_AccumulatedTranslationAdjustmentMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="us-gaap_ConcentrationRiskByBenchmarkAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_PowersimIncMember" xlink:label="altr_PowersimIncMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConvertibleNotesPayableCurrent" xlink:label="us-gaap_ConvertibleNotesPayableCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_DebtInstrumentCommencementOfInterestDate" xlink:label="altr_DebtInstrumentCommencementOfInterestDate"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleThresholdTradingDays" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdTradingDays"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities" xlink:label="us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherSundryLiabilitiesCurrent" xlink:label="us-gaap_OtherSundryLiabilitiesCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill" xlink:label="us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:label="us-gaap_NoncashInvestingAndFinancingItemsAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements" xlink:label="us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_PerpetualLicensesMember" xlink:label="altr_PerpetualLicensesMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingDisclosureTextBlock" xlink:label="us-gaap_SegmentReportingDisclosureTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CityAreaCode" xlink:label="dei_CityAreaCode"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_NCJudgementMember" xlink:label="altr_NCJudgementMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCashAndCashEquivalentsNoncurrent" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_OtherProductAndServiceMember" xlink:label="altr_OtherProductAndServiceMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SharesFairValueReclassificationsOfTemporaryToPermanentEquity" xlink:label="altr_SharesFairValueReclassificationsOfTemporaryToPermanentEquity"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpense" xlink:label="us-gaap_GeneralAndAdministrativeExpense"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GranteeStatusAxis" xlink:label="us-gaap_GranteeStatusAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_AccruedDefinedContributionPlanLiabilitiesCurrent" xlink:label="altr_AccruedDefinedContributionPlanLiabilitiesCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ClientEngineeringServicesSegmentMember" xlink:label="altr_ClientEngineeringServicesSegmentMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="dei_DocumentFiscalPeriodFocus"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedProfessionalFeesCurrent" xlink:label="us-gaap_AccruedProfessionalFeesCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConvertibleDebtTableTextBlock" xlink:label="us-gaap_ConvertibleDebtTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourMember" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased" xlink:label="us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MaintenanceMember" xlink:label="us-gaap_MaintenanceMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_WorldProgrammingMember" xlink:label="altr_WorldProgrammingMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_StockRepurchaseProgramRepurchaseAmount" xlink:label="altr_StockRepurchaseProgramRepurchaseAmount"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="us-gaap_AccountsReceivableNetCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain" xlink:label="srt_CumulativeEffectPeriodOfAdoptionDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="dei_EntityCommonStockSharesOutstanding"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherOperatingIncomeExpenseNet" xlink:label="us-gaap_OtherOperatingIncomeExpenseNet"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SoftwareRelatedServicesMember" xlink:label="altr_SoftwareRelatedServicesMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SummaryOfOtherIntangibleAssetsLineItems" xlink:label="altr_SummaryOfOtherIntangibleAssetsLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CoverAbstract" xlink:label="dei_CoverAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalYearFocus" xlink:label="dei_DocumentFiscalYearFocus"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingencyDamagesPaidValue" xlink:label="us-gaap_LossContingencyDamagesPaidValue"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ComprehensiveIncomeNoteTextBlock" xlink:label="us-gaap_ComprehensiveIncomeNoteTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OptionIndexedToIssuersEquityTypeDomain" xlink:label="us-gaap_OptionIndexedToIssuersEquityTypeDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAbstract" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxesReceivable" xlink:label="us-gaap_IncomeTaxesReceivable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SegmentReportingAbstract" xlink:label="us-gaap_SegmentReportingAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_SecurityExchangeName" xlink:label="dei_SecurityExchangeName"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="us-gaap_PreferredStockSharesIssued"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="us-gaap_PreferredStockSharesAuthorized"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CustomerRelationshipsMember" xlink:label="us-gaap_CustomerRelationshipsMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="us-gaap_PropertyPlantAndEquipmentGross"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="us-gaap_BusinessAcquisitionAcquireeDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossTax"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityEmergingGrowthCompany" xlink:label="dei_EntityEmergingGrowthCompany"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromConvertibleDebt" xlink:label="us-gaap_ProceedsFromConvertibleDebt"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_AmendmentFlag" xlink:label="dei_AmendmentFlag"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToUnderwriters" xlink:label="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToUnderwriters"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross" xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleTermsOfConversionFeature" xlink:label="us-gaap_DebtInstrumentConvertibleTermsOfConversionFeature"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_BusinessCombinationContingentConsiderationMarkToMarketAdjustments" xlink:label="altr_BusinessCombinationContingentConsiderationMarkToMarketAdjustments"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="us-gaap_TypeOfAdoptionMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_EffectiveIncomeTaxRateReconciliationReconcilingItemsDiscreteBenefitsAmount" xlink:label="altr_EffectiveIncomeTaxRateReconciliationReconcilingItemsDiscreteBenefitsAmount"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalizedContractCostNetNoncurrent" xlink:label="us-gaap_CapitalizedContractCostNetNoncurrent"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_PutRightExercisePeriod" xlink:label="altr_PutRightExercisePeriod"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFileNumber" xlink:label="dei_EntityFileNumber"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityExpirationDate1" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerRefundLiabilityCurrent" xlink:label="us-gaap_ContractWithCustomerRefundLiabilityCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:label="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_TwentyNineteenCreditAgreementMember" xlink:label="altr_TwentyNineteenCreditAgreementMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ChangeInPresentationOfCostsPolicyTextBlock" xlink:label="altr_ChangeInPresentationOfCostsPolicyTextBlock"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SupplementaryInformationAbstract" xlink:label="altr_SupplementaryInformationAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountsPayableCurrent" xlink:label="us-gaap_AccountsPayableCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_StockPurchaseAgreementMember" xlink:label="altr_StockPurchaseAgreementMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpenses" xlink:label="us-gaap_OperatingExpenses"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned" xlink:label="us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_MaintenanceAndOtherServicesMember" xlink:label="altr_MaintenanceAndOtherServicesMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_PrincipalAmountPlusAccruedAndUnpaidInterest" xlink:label="altr_PrincipalAmountPlusAccruedAndUnpaidInterest"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockValue" xlink:label="us-gaap_PreferredStockValue"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntitySmallBusiness" xlink:label="dei_EntitySmallBusiness"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityShellCompany" xlink:label="dei_EntityShellCompany"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromDebtNetOfIssuanceCosts" xlink:label="us-gaap_ProceedsFromDebtNetOfIssuanceCosts"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_EmployeeStockOptionAndEmployeeStockPurchasePlanMember" xlink:label="altr_EmployeeStockOptionAndEmployeeStockPurchasePlanMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareTextBlock" xlink:label="us-gaap_EarningsPerShareTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherSundryLiabilitiesNoncurrent" xlink:label="us-gaap_OtherSundryLiabilitiesNoncurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine1" xlink:label="dei_EntityAddressAddressLine1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SalesRevenueNetMember" xlink:label="us-gaap_SalesRevenueNetMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OptionIndexedToIssuersEquityTypeAxis" xlink:label="us-gaap_OptionIndexedToIssuersEquityTypeAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilitiesCurrent" xlink:label="us-gaap_OtherLiabilitiesCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="us-gaap_FiniteLivedIntangibleAssetsGross"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFrequencyOfPeriodicPayment" xlink:label="us-gaap_DebtInstrumentFrequencyOfPeriodicPayment"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="us-gaap_DepreciationDepletionAndAmortization"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ProductOrServiceAxis" xlink:label="srt_ProductOrServiceAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent" xlink:label="us-gaap_ContractWithCustomerLiabilityNoncurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_Security12bTitle" xlink:label="dei_Security12bTitle"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioPreviouslyReportedMember" xlink:label="srt_ScenarioPreviouslyReportedMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TemporaryEquityCarryingAmountAttributableToParent" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToParent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTextBlock" xlink:label="us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingencyDamagesAwardedValue" xlink:label="us-gaap_LossContingencyDamagesAwardedValue"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember" xlink:label="us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountingChangesAndErrorCorrectionsAbstract" xlink:label="us-gaap_AccountingChangesAndErrorCorrectionsAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCredit" xlink:label="us-gaap_LineOfCredit"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ClientEngineeringServicesMember" xlink:label="altr_ClientEngineeringServicesMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseDebt" xlink:label="us-gaap_InterestExpenseDebt"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfOtherNonoperatingIncomeExpenseTableTextBlock" xlink:label="us-gaap_ScheduleOfOtherNonoperatingIncomeExpenseTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="us-gaap_CommonStockSharesOutstanding"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccruedRoyaltiesCurrent" xlink:label="us-gaap_AccruedRoyaltiesCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionByUniqueDescriptionAxis" xlink:label="us-gaap_DebtConversionByUniqueDescriptionAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SupplementalCashFlowElementsAbstract" xlink:label="us-gaap_SupplementalCashFlowElementsAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="us-gaap_ConcentrationRiskTypeDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessCombinationAndAssetAcquisitionAbstract" xlink:label="us-gaap_BusinessCombinationAndAssetAcquisitionAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentType" xlink:label="dei_DocumentType"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountingStandardsUpdate202006Member" xlink:label="us-gaap_AccountingStandardsUpdate202006Member"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentQuarterlyReport" xlink:label="dei_DocumentQuarterlyReport"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock" xlink:label="us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ScheduleOfIncomeTaxExpenseBenefitAndEffectiveTaxRateTableTextBlock" xlink:label="altr_ScheduleOfIncomeTaxExpenseBenefitAndEffectiveTaxRateTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxesAndTaxCredits" xlink:label="us-gaap_DeferredIncomeTaxesAndTaxCredits"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFilerCategory" xlink:label="dei_EntityFilerCategory"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCurrentLiabilitiesTableTextBlock" xlink:label="us-gaap_OtherCurrentLiabilitiesTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_CurrencyLossesOnAcquisitionRelatedIntercompanyLoans" xlink:label="altr_CurrencyLossesOnAcquisitionRelatedIntercompanyLoans"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="us-gaap_BalanceSheetLocationDomain"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_GainOnMarkToMarketAdjustmentOfContingentConsideration" xlink:label="altr_GainOnMarkToMarketAdjustmentOfContingentConsideration"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentAssets" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SummaryOfOtherIntangibleAssetsTable" xlink:label="altr_SummaryOfOtherIntangibleAssetsTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SecuredCreditAgreementMember" xlink:label="altr_SecuredCreditAgreementMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_DebtInstrumentConvertibleConversionRatePrincipalAmount" xlink:label="altr_DebtInstrumentConvertibleConversionRatePrincipalAmount"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TradeNamesMember" xlink:label="us-gaap_TradeNamesMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="us-gaap_NonoperatingIncomeExpense"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid" xlink:label="us-gaap_CapitalExpendituresIncurredButNotYetPaid"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities" xlink:label="us-gaap_Liabilities"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_SpecialAdjustmentsInterestIncomeAndOther" xlink:label="altr_SpecialAdjustmentsInterestIncomeAndOther"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_DebtInstrumentPrincipalOutstanding" xlink:label="altr_DebtInstrumentPrincipalOutstanding"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" xlink:label="us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProductConcentrationRiskMember" xlink:label="us-gaap_ProductConcentrationRiskMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:label="us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentsTextBlock" xlink:label="us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentsTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense" xlink:label="us-gaap_InterestExpense"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfConvertibleDebt" xlink:label="us-gaap_RepaymentsOfConvertibleDebt"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ContractWithCustomerAssetNetCurrent" xlink:label="us-gaap_ContractWithCustomerAssetNetCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRepurchasedFaceAmount" xlink:label="us-gaap_DebtInstrumentRepurchasedFaceAmount"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_InterestIncomeAndOther" xlink:label="altr_InterestIncomeAndOther"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoncashOrPartNoncashAcquisitionsTable" xlink:label="us-gaap_NoncashOrPartNoncashAcquisitionsTable"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentRedemptionPricePercentage" xlink:label="us-gaap_DebtInstrumentRedemptionPricePercentage"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UseOfEstimates" xlink:label="us-gaap_UseOfEstimates"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureTextBlock" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestAndOtherIncome" xlink:label="us-gaap_InterestAndOtherIncome"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesOneMember" xlink:label="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesOneMember"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseDebtExcludingAmortization" xlink:label="us-gaap_InterestExpenseDebtExcludingAmortization"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="us-gaap_DisaggregationOfRevenueLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="us-gaap_LeaseholdImprovementsMember"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_BusinessCombinationEstimatedPostCombinationExpense" xlink:label="altr_BusinessCombinationEstimatedPostCombinationExpense"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_CashPaidForRepurchaseAndRetirementOfCommonStock" xlink:label="altr_CashPaidForRepurchaseAndRetirementOfCommonStock"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:label="us-gaap_FairValueDisclosuresAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ReclassificationsOfTemporaryToPermanentEquity" xlink:label="us-gaap_ReclassificationsOfTemporaryToPermanentEquity"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RestatementDomain" xlink:label="srt_RestatementDomain"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="us-gaap_BusinessAcquisitionAxis"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureAbstract" xlink:label="us-gaap_IncomeTaxDisclosureAbstract"/>
<link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
<link:loc xlink:type="locator" xlink:href="altr-20230930.xsd#altr_EmployeeStockPurchasePlanLiabilities" xlink:label="altr_EmployeeStockPurchasePlanLiabilities"/>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Collaborative Arrangement and Arrangement Other than Collaborative </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Collaborative Arrangement and Arrangement Other than Collaborative [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Document Transition Report </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Document Transition Report </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average remaining contractual term (years), Outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Contracted revenue not yet recognized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revenue, Remaining Performance Obligation, Amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestOnConvertibleDebtNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Interest expense related to Convertible Notes, net of tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestOnConvertibleDebtNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Interest on Convertible Debt, Net of Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_GoodwillAffectOfForeignCurrencyTranslationGainLossAndOther_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Foreign currency translation and other </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_GoodwillAffectOfForeignCurrencyTranslationGainLossAndOther_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Goodwill Affect Of Foreign Currency Translation Gain Loss And Other </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_GoodwillAffectOfForeignCurrencyTranslationGainLossAndOther_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Goodwill affect of foreign currency translation gain (loss) and other. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other long-term liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Liabilities, Noncurrent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule Of Segment Reporting Information By Segment [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Segment Reporting Information, by Segment [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Prepaid expenses and other current assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Increase (Decrease) in Prepaid Expense and Other Assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockUnitsRSUMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Restricted Stock Units (RSUs) [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockUnitsRSUMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Restricted Stock Units (RSUs) [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AccruedObligationsForAcquisitionOfBusinesses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Obligations for acquisition of businesses and technology </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AccruedObligationsForAcquisitionOfBusinesses_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accrued Obligations For Acquisition Of Businesses </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AccruedObligationsForAcquisitionOfBusinesses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Accrued obligations for acquisition of businesses. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareRelatedServiceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Software Related Services [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareRelatedServiceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Software Related Service [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareRelatedServiceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Software related service. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Fair Value Measurements </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Fair Value Disclosures [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Revenue </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Total revenue </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revenue from Contract with Customer, Excluding Assessed Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AccountsReceivableNetCurrentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accounts Receivable [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AccountsReceivableNetCurrentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accounts Receivable Net Current [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AccountsReceivableNetCurrentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Accounts receivable net current. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ComputerEquipmentAndSoftwareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Computer Equipment and Software [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ComputerEquipmentAndSoftwareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Computer Equipment And Software [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ComputerEquipmentAndSoftwareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Computer equipment and software. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Compensation cost related to nonvested awards not yet recognized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule of Disaggregation of Revenue </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Disaggregation of Revenue [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Payments to Acquire Businesses, Net of Cash Acquired, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Payments for acquisition of businesses, net of cash acquired </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Payments to Acquire Businesses, Net of Cash Acquired </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Concentration Risk Type [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Deferred revenue </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Contract with Customer, Liability, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Summary of Amounts of Identified Assets Acquired and Liabilities Assumed at the Acquisition Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PaymentsForRepurchaseOfCommonStockShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Payments for repurchase of common stock, Shares </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PaymentsForRepurchaseOfCommonStockShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Payments for Repurchase of Common Stock Shares </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PaymentsForRepurchaseOfCommonStockShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Payments for repurchase of common stock shares. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepositLiabilitiesAccruedInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Deposit Liabilities, Accrued Interest </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepositLiabilitiesAccruedInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accrued interest </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleDebtFairValueDisclosures_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Fair value of convertible notes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleDebtFairValueDisclosures_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Convertible Debt, Fair Value Disclosures </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillAcquiredDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Acquisitions </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillAcquiredDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Goodwill, Acquired During Period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TemporaryEquitySharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Shares issued </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TemporaryEquitySharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Temporary Equity, Shares Issued </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoncashOrPartNoncashAcquisitionsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Noncash or Part Noncash Acquisitions [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Operating lease liabilities, net of current portion </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Operating Lease, Liability, Noncurrent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandTwentyThreeAcquisitionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> 2023 Acquisitions [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandTwentyThreeAcquisitionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Two Thousand Twenty Three Acquisitions [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandTwentyThreeAcquisitionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Two Thousand Twenty Three Acquisitions [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Balance Sheet Location </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Balance Sheet Location [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Total current assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Assets, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Liabilities and Equity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Address, State or Province </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Address, State or Province </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_LitigationCaseTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Litigation Case </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_LitigationCaseTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Litigation Case [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Deferred tax assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Deferred Income Tax Assets, Net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TermLicensesAndOtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Term licenses and other [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TermLicensesAndOtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Term Licenses And Other [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TermLicensesAndOtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Term licenses and other. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Number of options, Outstanding, Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Number of options, Outstanding, Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Comprehensive Income (Loss), Net of Tax, Attributable to Parent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Comprehensive loss </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockIssuedDuringPeriodSharesPrivatePlacementNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Stock issued during period shares private placement new issues. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockIssuedDuringPeriodSharesPrivatePlacementNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Issued During Period Shares Private Placement New Issues </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockIssuedDuringPeriodSharesPrivatePlacementNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Issuance of common stock in private placement, net of issuance costs (in shares) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Trading Symbol </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Trading Symbol </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Common stock, shares issued </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Common Stock, Shares, Issued </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Reconciliation of Cash, Cash Equivalents and Restricted Cash </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Restrictions on Cash and Cash Equivalents [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule of Interest Expense Related to Convertible Notes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Interest Income and Interest Expense Disclosure [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DocumentAndEntityInformationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Document And Entity Information [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DocumentAndEntityInformationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Document And Entity Information [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DocumentAndEntityInformationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Document and entity information table. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Prepaid expenses and other current assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Prepaid Expense and Other Assets, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLossAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Numerator: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLossAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Net Income (Loss) Attributable to Parent [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingAndMarketingExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Sales and marketing [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingAndMarketingExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Sales and Marketing Expense [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingAndMarketingExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Selling and Marketing Expense [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt Instrument [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Long-Term Debt Instruments [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Beginning balance (in shares) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Ending balance (in shares) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Shares, Outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Amount available for future borrowing </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Line of Credit Facility, Remaining Borrowing Capacity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Common stock reserved for issuance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Common Stock, Capital Shares Reserved for Future Issuance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accumulated Other Comprehensive Loss [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> AOCI Attributable to Parent [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Acquisitions </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Business Combination Disclosure [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Total other comprehensive loss </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Comprehensive Income (Loss), Net of Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accumulated Other Comprehensive Income (Loss) [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accumulated Other Comprehensive Income (Loss) [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Address, City or Town </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Address, City or Town </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Convertible notes holders conversion rights under circumstances two [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Convertible Notes Holders Conversion Rights Under Circumstances Two [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Convertible notes holders conversion rights under circumstances two [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockRepurchaseProgramAveragePricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Stock repurchase program, Average price per share </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockRepurchaseProgramAveragePricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Repurchase Program Average Price Per Share </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockRepurchaseProgramAveragePricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Stock repurchase program average price per share. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Disclosure [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Summary of Property and Equipment </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Property, Plant and Equipment [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Subsequent Event [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Subsequent Event [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Subsequent Event Type [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_RightOfUseAssetsUnderFinanceLeasesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Right-of-Use Assets Under Finance Leases [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_RightOfUseAssetsUnderFinanceLeasesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Right Of Use Assets Under Finance Leases [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_RightOfUseAssetsUnderFinanceLeasesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Right-of-use assets under finance leases. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Additional Paid-In Capital [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Additional Paid-in Capital [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> CURRENT LIABILITIES: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Liabilities, Current [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> CURRENT ASSETS: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Assets, Current [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Preferred stock, par value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Preferred Stock, Par or Stated Value Per Share </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Amounts reclassified from accumulated other comprehensive income </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Statement of Stockholders' Equity [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Current portion of operating lease liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Operating Lease, Liability, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument maturity date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Maturity Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Property and equipment, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Property and equipment, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Property, Plant and Equipment, Net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PromissoryNotesIssuedAndDeferredPaymentObligationsForAcquisitions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Deferred payment obligations for acquisitions and investments </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PromissoryNotesIssuedAndDeferredPaymentObligationsForAcquisitions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Promissory notes issued and deferred payment obligations for acquisitions. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PromissoryNotesIssuedAndDeferredPaymentObligationsForAcquisitions_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Promissory Notes Issued And Deferred Payment Obligations For Acquisitions </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Class of Stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Class of Stock [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Restructuring Charges, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Restructuring expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Restructuring charges </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Restructuring Charges </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PaymentForRepurchaseOfCommonStockShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Payment For Repurchase Of Common Stock Shares </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PaymentForRepurchaseOfCommonStockShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Payment for repurchase of common stock shares. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PaymentForRepurchaseOfCommonStockShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Repurchase and retirement of common stock, Shares </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationContingentConsiderationLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Business acquisition, Contingent consideration liability </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationContingentConsiderationLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Business Combination, Contingent Consideration, Liability, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationContingentConsiderationLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Contingent consideration </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationContingentConsiderationLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Business Combination, Contingent Consideration, Liability </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Statement of Comprehensive Income [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Collaborative Arrangement and Arrangement Other than Collaborative </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Collaborative Arrangement and Arrangement Other than Collaborative [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Central Index Key </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Central Index Key </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherIntangibleAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other Intangibles [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherIntangibleAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Intangible Assets [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Plan Name </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Plan Name [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Change in Accounting Principle, Accounting Standards Update, Adopted [true false] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Change in Accounting Principle, Accounting Standards Update, Adopted [true false] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Liabilities Disclosure [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandAndSeventeenEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> 2017 Plan [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandAndSeventeenEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Two Thousand And Seventeen Equity Incentive Plan [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandAndSeventeenEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Two thousand and seventeen equity incentive plan. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SalesCommissionsAndFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Sales commissions </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SalesCommissionsAndFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Sales Commissions and Fees </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Preferred Stock, Shares Outstanding, Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Preferred Stock, Shares Outstanding, Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Preferred stock, shares outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Preferred Stock, Shares Outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Revenue, remaining contractual obligation, expected to recognize, period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfGoodwillTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Changes in Carrying Amount of Goodwill Attributable to Software Reporting Segment </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfGoodwillTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Goodwill [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Total current liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Liabilities, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Tax Identification Number </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Tax Identification Number </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Loss before income taxes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Changes in assets and liabilities: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Increase (Decrease) in Operating Capital [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDebtIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Payments of Debt Issuance Costs </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDebtIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Payments of debt issuance costs </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConceptEngineeringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Concept Engineering [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConceptEngineeringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Concept Engineering [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConceptEngineeringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Concept Engineering member. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Additional Disclosures [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Denominator: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Weighted Average Number of Shares Outstanding Reconciliation [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ProfessionalSoftwareServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Professional software services [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ProfessionalSoftwareServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Professional Software Services [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ProfessionalSoftwareServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Professional software services. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourAndTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Convertible Senior Notes Due in 2024 and 2027 [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourAndTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Convertible Senior Notes Due In Two Thousand Twenty Four And Two Thousand Twenty Seven [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourAndTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Convertible Senior Notes Due In Two Thousand Twenty Four And Two Thousand Twenty Seven. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Issuance of common stock for employee stock purchase program </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Issued During Period, Value, Employee Stock Purchase Plan </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Plan Name </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Plan Name [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> TOTAL ASSETS </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_RevenueFromContractsWithCustomersLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Revenue From Contracts With Customers [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_RevenueFromContractsWithCustomersLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revenue From Contracts With Customers [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_RevenueFromContractsWithCustomersLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Revenue from contracts with customers. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Operating lease right of use assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Operating Lease, Right-of-Use Asset </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonClassAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Class A Common Stock [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonClassAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Common Class A [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Registrant Name </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Registrant Name </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Debt Issuance Costs, Net, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Less: unamortized debt issuance costs </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Issuance Costs, Net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Software [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Software Member </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Retained Earnings (Accumulated Deficit), Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accumulated deficit </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Retained Earnings (Accumulated Deficit) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Supplemental disclosure of cash flow: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Supplemental Cash Flow Information [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_NumberOfPriorBusinessAcquistionsValuationFinalized_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Number of prior business acquistions, valuation finalized. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_NumberOfPriorBusinessAcquistionsValuationFinalized_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Number Of Prior Business Acquistions, Valuation Finalized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_NumberOfPriorBusinessAcquistionsValuationFinalized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Number of prior business acquistions for which valuation is finalized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accumulated Deficit [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Retained Earnings [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementClassOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Class of Stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementClassOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Class of Stock [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Number of RSUs, Outstanding Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Number of RSUs, Outstanding Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxLiabilitiesNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Deferred tax liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxLiabilitiesNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Deferred Income Tax Liabilities, Net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Issuance of common stock for employee stock purchase program (in shares) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Issued During Period, Shares, Employee Stock Purchase Plans </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Minimum [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Minimum [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Proceeds from the exercise of common stock options </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Proceeds from Stock Options Exercised </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Significant Accounting Policies </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Significant Accounting Policies [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedIncomeTaxesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Income taxes payable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedIncomeTaxesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accrued Income Taxes, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Equity Component </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Equity Component [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementBusinessSegmentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> CES [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementBusinessSegmentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Segments [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConversionOfStockSharesConverted1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Conversion from Class B to Class A common stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConversionOfStockSharesConverted1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Conversion of Stock, Shares Converted </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Change in Accounting Principle, Accounting Standards Update, Adoption Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Change in Accounting Principle, Accounting Standards Update, Adoption Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LandMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Land [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LandMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Land [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonstock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument, convertible, principal amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonstock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument Principal Amount Denomination For Conversion Into CommonStock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonstock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Debt instrument principal amount denomination for conversion into commonStock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Amortization of Debt Issuance Costs and Discounts, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Amortization of debt issuance costs and discount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Amortization of Debt Issuance Costs and Discounts </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Amortization of debt issuance costs </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Adjustments to reconcile net loss to net cash provided by operating activities: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_FurnitureEquipmentAndOtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Furniture Equipment and Other [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_FurnitureEquipmentAndOtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Furniture Equipment And Other [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_FurnitureEquipmentAndOtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Furniture equipment and other. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Disclosure [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BuildingAndBuildingImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Building and Improvements [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BuildingAndBuildingImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Building and Building Improvements [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AmountWithheldOnBehalfOfEmployeesForFuturePurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Amount withheld on behalf of employees for a future purchase </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AmountWithheldOnBehalfOfEmployeesForFuturePurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Amount Withheld On Behalf Of Employees For Future Purchase </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AmountWithheldOnBehalfOfEmployeesForFuturePurchase_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Amount withheld on behalf of employees for future purchase. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Current Reporting Status </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Current Reporting Status </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other financing activities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Proceeds from (Payments for) Other Financing Activities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Common stock, shares authorized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Common Stock, Shares Authorized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PutOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Put Option [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandAndTwentyOneEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> 2021 Employee Stock Purchase Plan [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandAndTwentyOneEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Two Thousand And Twenty One Employee Stock Purchase Plan [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandAndTwentyOneEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Two thousand and twenty one employee stock purchase plan. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Research and Development Expense, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Research and development </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Research and Development Expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByBalanceSheetGroupingTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Fair Value, by Balance Sheet Grouping [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_RevenueFromContractsWithCustomersTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revenue From Contracts With Customers [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_RevenueFromContractsWithCustomersTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Revenue from contracts with customers. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Shares authorized to be repurchased amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Repurchase Program, Authorized Amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfIntangibleAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Amortization of intangible assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfIntangibleAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Amortization of Intangible Assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfIntangibleAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel"> Amortization of intangible assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Common stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Common Stock, Value, Issued </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument convertible initial conversion price per share of common stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Convertible, Conversion Price </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncashIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Other Noncash Income (Expense), Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncashIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Other, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncashIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Noncash Income (Expense) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Convertible Senior Notes Due in 2027 [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Convertible Senior Notes Due In Two Thousand Twenty Seven [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentySevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Convertible senior notes due in two thousand twenty seven. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Deferred revenue, revenue recognized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Contract with Customer, Liability, Revenue Recognized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Current Fiscal Year End Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Current Fiscal Year End Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Share-Based Payment Arrangement, Noncash Expense, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Stock-based compensation expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Total stock-based compensation expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Stock-based compensation expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement, Noncash Expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockPurchaseProgramSharesAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Number of shares repurchased </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockPurchaseProgramSharesAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Purchase Program Shares Acquired </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockPurchaseProgramSharesAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Stock purchase program shares acquired. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Operating loss </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Operating Income (Loss) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Business acquisition, Equity interest issued, Number of shares </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Business Acquisition, Equity Interest Issued or Issuable, Number of Shares </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Income tax (benefit) expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Income tax (benefit) expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Income Tax Expense (Benefit), Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Income Tax Expense (Benefit) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Research and development [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Research and Development Expense [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleLongTermNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> 2027 Convertible senior notes, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleLongTermNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Net carrying amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleLongTermNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Convertible senior notes, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleLongTermNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Convertible Notes Payable, Noncurrent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NatureOfOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Organization and Description of Business </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NatureOfOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Nature of Operations [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesAcquisitions_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Issued During Period, Shares, Acquisitions </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesAcquisitions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Issuance of common stock for acquisitions (in shares) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskPercentage1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Percentage of net revenues through indirect channels </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskPercentage1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Concentration Risk, Percentage </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Stock-based compensation expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement, Expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Indefinite-lived Intangible Assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Indefinite-Lived Intangible Assets [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ProceedsFromEmployeeStockPurchasePlanContributions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Proceeds from employee stock purchase plan contributions </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ProceedsFromEmployeeStockPurchasePlanContributions_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Proceeds From Employee Stock Purchase Plan Contributions </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ProceedsFromEmployeeStockPurchasePlanContributions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Proceeds from employee stock purchase plan contributions. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Disaggregation Of Revenue [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Disaggregation of Revenue [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLossAttributableToParentDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Numerator for diluted loss per share </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLossAttributableToParentDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Net Income (Loss) Attributable to Parent, Diluted </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Finite-Lived Intangible Assets, Net, Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Finite-Lived Intangible Assets, Net, Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Net carrying amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Finite-Lived Intangible Assets, Net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule of Segment Reporting Information </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Segment Reporting Information, by Segment [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Income taxes paid </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Income Taxes Paid </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Revenue from Contracts with Customers </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revenue from Contract with Customer [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Comprehensive Income (Loss), Net of Tax [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other comprehensive (loss) income, net of tax: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Effect of exchange rate changes on cash, cash equivalents and restricted cash </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Effect of Exchange Rate on Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Continuing Operations </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Aggregate intrinsic value, Outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LicenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> License [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LicenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> License [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument, aggregate principal amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Face Amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Principal </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToInitialPurchaser_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Additional principal amount of notes to initial purchaser's </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToInitialPurchaser_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Option to Purchase Additional Principal Amount of Notes to Initial Purchaser </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToInitialPurchaser_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Option to purchase additional principal amount of notes to initial purchaser. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Cumulative Effect, Period of Adoption, Adjustment [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Cumulative Effect, Period of Adoption, Adjustment [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_LineOfCreditFacilityIncreaseInBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Increase in line of credit borrowing capacity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_LineOfCreditFacilityIncreaseInBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Line Of Credit Facility Increase In Borrowing Capacity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_LineOfCreditFacilityIncreaseInBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Line Of Credit Facility Increase In Borrowing Capacity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Operating expenses: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Operating Expenses [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Property, Plant and Equipment [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SettlementOfConvertibleSeniorNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Settlement of convertible senior notes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SettlementOfConvertibleSeniorNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Settlement of Convertible Senior Notes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SettlementOfConvertibleSeniorNotes_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Settlement of convertible senior notes. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_FairValueExpenseRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Expense on repurchase of convertible senior notes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_FairValueExpenseRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Fair value expense recognized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_FairValueExpenseRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Fair Value Expense Recognized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_FairValueExpenseRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Fair value expense recognized. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Commitments and Contingencies Disclosure [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other long-term assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Assets, Noncurrent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleIfConvertedValueInExcessOfPrincipal_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument, convertible, "if-converted value" in excess of the principal amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleIfConvertedValueInExcessOfPrincipal_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Convertible, If-converted Value in Excess of Principal </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Number of options, Granted </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Depreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Depreciation, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Depreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Depreciation expense, including amortization of right-of-use assets under finance leases </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Depreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Depreciation </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Interest paid </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Interest Paid, Excluding Capitalized Interest, Operating Activities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonClassBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Class B Common Stock [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonClassBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Common Class B [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentConvertibleThresholdBusinessDays_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument, convertible, business days </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentConvertibleThresholdBusinessDays_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument Convertible Threshold Business Days </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentConvertibleThresholdBusinessDays_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Debt instrument convertible threshold business days. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> STOCKHOLDERS’ EQUITY: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Equity, Attributable to Parent [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DocumentAndEntityInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Document And Entity Information [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DocumentAndEntityInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Document And Entity Information [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DocumentAndEntityInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Document and entity information. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DevelopedTechnologyRightsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Developed Technology [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DevelopedTechnologyRightsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Developed Technology Rights [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Contracted revenue recognize percentage </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revenue, Remaining Performance Obligation, Percentage </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostOfGoodsAndServicesSold_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Cost of Goods and Services Sold, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostOfGoodsAndServicesSold_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Total cost of revenue </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostOfGoodsAndServicesSold_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Cost of Goods and Services Sold </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Adjusted EBITDA </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Adjusted Earnings Before Interest Taxes Depreciation And Amortization </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Adjusted earnings before interest taxes depreciation and amortization. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ScheduleOfOtherIntangibleAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule of Other Intangible Assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ScheduleOfOtherIntangibleAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule Of Other Intangible Assets Table [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ScheduleOfOtherIntangibleAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Schedule of Other Intangible Assets [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Loss per share: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Earnings Per Share [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Indefinite-lived Intangible Assets, Major Class Name </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Indefinite-Lived Intangible Assets, Major Class Name [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ExpenseOnRepurchaseOfConvertibleSeniorNote_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Expense on repurchase of convertible senior notes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ExpenseOnRepurchaseOfConvertibleSeniorNote_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Expense On Repurchase Of Convertible Senior Note </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ExpenseOnRepurchaseOfConvertibleSeniorNote_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Expense on repurchase of convertible senior note. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Loss Contingencies [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Loss Contingencies [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_LitigationCaseAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Litigation Case </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_LitigationCaseAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Litigation Case [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Segments </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Segments [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LicenseAndServiceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Total Software and Related Services [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LicenseAndServiceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> License and Service [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Share Based Compensation Arrangement By Share Based Payment Award [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncurrentAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other Long-Term Assets [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncurrentAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Noncurrent Assets [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareSegmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Software [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareSegmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Software Segment [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareSegmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Software. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Earnings Per Share, Basic, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Earnings Per Share, Basic </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Net loss per share attributable to common stockholders, basic </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSharesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Convertible Shares [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSharesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Convertible shares. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Components of Accumulated Other Comprehensive Loss </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Commitments and contingencies </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Commitments and Contingencies </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Income Statement [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Indefinite-Lived Intangible Assets (Excluding Goodwill), Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Indefinite-Lived Intangible Assets (Excluding Goodwill), Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Indefinite-Lived Intangible Assets (Excluding Goodwill), Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Net carrying amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Indefinite-Lived Intangible Assets (Excluding Goodwill) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalizedContractCostNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Capitalized contract cost net, current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalizedContractCostNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Capitalized Contract Cost, Net, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Statistical Measurement </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Statistical Measurement [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Loss Contingencies [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Loss Contingencies [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Net cash provided by operating activities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Net Cash Provided by (Used in) Operating Activities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Document Period End Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Document Period End Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Statistical Measurement </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Statistical Measurement [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt Conversion, Name </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Conversion, Name [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Commitments and Contingencies </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Commitments and Contingencies Disclosure [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Earnings Per Share, Diluted, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Earnings Per Share, Diluted </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Net loss per share attributable to common stockholders, diluted </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductsAndServicesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Product and Service </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductsAndServicesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Product and Service [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_CurrencyGainsOnAcquisitionRelatedIntercompanyLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Currency gains on acquisition related intercompany loans. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_CurrencyGainsOnAcquisitionRelatedIntercompanyLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Currency Gains On Acquisition Related Intercompany Loans </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_CurrencyGainsOnAcquisitionRelatedIntercompanyLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Currency gains on acquisition-related intercompany loans </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostOfSalesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Cost of revenue - software [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostOfSalesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Cost of Sales [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Foreign currency translation, tax effect </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskBenchmarkDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Concentration Risk Benchmark [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Weighted average remaining service period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Stock-based compensation recognized service period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Award Requisite Service Period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revenue from Contract with Customer [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Retirement related benefit plans, tax effect </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt Instrument, Name </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Name [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SupplementaryInformationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Supplementary Information </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SupplementaryInformationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Supplementary Information [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SupplementaryInformationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Supplementary information. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Number of options, Exercisable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockIssuedDuringPeriodValuePrivatePlacementNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Stock issued during period value private placement new issues. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockIssuedDuringPeriodValuePrivatePlacementNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Issued During Period Value Private Placement New Issues </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockIssuedDuringPeriodValuePrivatePlacementNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Issuance of common stock in private placement, net of issuance costs </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument, description </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Description </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Number of reportable segments </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Number of Reportable Segments </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Retirement Related Benefit Plans [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Additional paid-in capital </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Additional Paid in Capital, Common Stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SalesAndExciseTaxPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accrued VAT </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SalesAndExciseTaxPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Sales and Excise Tax Payable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Foreign exchange loss </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Foreign Currency Transaction Gain (Loss), before Tax, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Gain (Loss), Foreign Currency Transaction, before Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRepurchaseOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Payments for Repurchase of Common Stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRepurchaseOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Repurchase and retirement of common stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Finite-Lived Intangible Assets, Major Class Name </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Finite-Lived Intangible Assets, Major Class Name [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Liability, Pension and Other Postretirement and Postemployment Benefits, Noncurrent, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Pension and other post retirement liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Liability, Pension and Other Postretirement and Postemployment Benefits, Noncurrent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_NumberOfEqualVestingInstallments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Number of vesting equal annual installments </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_NumberOfEqualVestingInstallments_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Number Of Equal Vesting Installments </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_NumberOfEqualVestingInstallments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Number of equal vesting installments. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Number of options, Exercised </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Exercise of stock options (in shares) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_LossOnMarkToMarketAdjustmentOfContingentConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Loss On Mark To Market Adjustment Of Contingent Consideration </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_LossOnMarkToMarketAdjustmentOfContingentConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Loss on mark to market adjustment of contingent consideration. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_LossOnMarkToMarketAdjustmentOfContingentConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Loss (gain) on mark-to-market adjustment of contingent consideration </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_LossOnMarkToMarketAdjustmentOfContingentConsideration_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Loss (gain) on mark-to-market adjustment of contingent consideration </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LicenseAndMaintenanceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Total Software [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LicenseAndMaintenanceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> License and Maintenance [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> LIABILITIES, MEZZANINE EQUITY AND STOCKHOLDERS’ EQUITY </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Liabilities and Equity [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncurrentLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Summary of Other Long-term Liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncurrentLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Noncurrent Liabilities [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueAcquisitions_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Issued During Period, Value, Acquisitions </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueAcquisitions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Issuance of common stock for acquisitions </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Address, Postal Zip Code </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Address, Postal Zip Code </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Interactive Data Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Interactive Data Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingAndMarketingExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Selling and Marketing Expense, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingAndMarketingExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Sales and marketing </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingAndMarketingExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Selling and Marketing Expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandTwentyOneAcquisitionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> 2021 Acquisitions [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandTwentyOneAcquisitionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Two Thousand Twenty One Acquisitions [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwoThousandTwentyOneAcquisitionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Two thousand twenty one acquisitions. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GranteeStatusDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Grantee Status </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GranteeStatusDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Grantee Status [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument, convertible, consecutive trading days </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Convertible, Threshold Consecutive Trading Days </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Increase (Decrease) in Accounts Payable, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accounts payable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Increase (Decrease) in Accounts Payable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Increase (Decrease) in Employee Related Liabilities, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accrued compensation and benefits </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Increase (Decrease) in Employee Related Liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RestatementAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Recast [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RestatementAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revision of Prior Period, Adjustment [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Equity [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShortTermDebtTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Short-Term Debt [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TheTimingOfPayrollDeductionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> The Timing of Payroll Deductions [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TheTimingOfPayrollDeductionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> The Timing Of Payroll Deductions [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TheTimingOfPayrollDeductionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> The timing of payroll deductions. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Number of RSUs, Granted </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RestatementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revision of Prior Period [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average exercise price per share, Exercised </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Incorporation, State or Country Code </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Incorporation, State or Country Code </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Equity Components </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Equity Components [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Increase (Decrease) in Accounts Receivable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Accounts receivable, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Non-income tax liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accrual for Taxes Other than Income Taxes, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Increase (Decrease) in Other Operating Liabilities, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other accrued expenses and current liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Increase (Decrease) in Other Operating Liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllOtherSegmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> All Other [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllOtherSegmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Segments [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentConvertibleThresholdMaximumPercentageOfProductOfLastReportedSalePriceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument, convertible, maximum threshold percentage of sale price of common stock during measurement period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentConvertibleThresholdMaximumPercentageOfProductOfLastReportedSalePriceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument Convertible Threshold Maximum Percentage Of Product Of Last Reported Sale Price Of Common Stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentConvertibleThresholdMaximumPercentageOfProductOfLastReportedSalePriceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Debt instrument convertible threshold maximum percentage of product of last reported sale price of common stock. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Recent Accounting Guidance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accounting Standards Update and Change in Accounting Principle [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Local Phone Number </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Local Phone Number </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Property, Plant and Equipment [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Property, Plant and Equipment [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average exercise price per share, Exercisable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt conversion, converted instrument, shares issued </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Conversion, Converted Instrument, Shares Issued </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Vesting of restricted stock (in shares) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Goodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Goodwill, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Goodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Goodwill </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Goodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Goodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Goodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Goodwill </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Repayments of notes payable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Repayments of Notes Payable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Statement of Cash Flows [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TemporaryEquityRedemptionPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Put right, exercise price </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TemporaryEquityRedemptionPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Temporary Equity, Redemption Price Per Share </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Organization, Consolidation and Presentation of Financial Statements [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Accumulated Other Comprehensive Income (Loss), Net of Tax, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accumulated other comprehensive loss </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accumulated Other Comprehensive Income (Loss), Net of Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Segment Reporting Information [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Segment Reporting Information [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GrossProfit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Gross profit </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GrossProfit_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Gross Profit </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedTranslationAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Foreign Currency Translation [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedTranslationAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accumulated Foreign Currency Adjustment Attributable to Parent [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskByBenchmarkAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Concentration Risk Benchmark [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Common stock, par value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Common Stock, Par or Stated Value Per Share </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument interest rate </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Interest Rate, Stated Percentage </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Cumulative Effect, Period of Adoption </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Cumulative Effect, Period of Adoption [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average period of recognition </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Long-Lived Tangible Asset </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Long-Lived Tangible Asset [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PowersimIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Powersim Inc [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PowersimIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Powersim Inc [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PowersimIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Powersim Inc Member. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleNotesPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Net carrying amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleNotesPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Convertible Notes Payable, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleNotesPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Current portion of convertible senior notes, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Maximum [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Maximum [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentCommencementOfInterestDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Interest payment commencement date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentCommencementOfInterestDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument Commencement Of Interest Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentCommencementOfInterestDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Debt instrument commencement of interest date. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdTradingDays_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument, convertible, trading days </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdTradingDays_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Convertible, Threshold Trading Days </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Consideration for the business acquisition </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement, Additional Disclosure [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> APIC, Share-Based Payment Arrangement, Increase for Cost Recognition, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Stock-based compensation </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> APIC, Share-Based Payment Arrangement, Increase for Cost Recognition </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Net increase (decrease) in cash, cash equivalents and restricted cash </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromOtherInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Other investing activities, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromOtherInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Payments for (Proceeds from) Other Investing Activities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherSundryLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other current liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherSundryLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Sundry Liabilities, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> General and administrative [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> General and Administrative Expense [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IntangibleAssetsGrossExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Intangible Assets, Gross (Excluding Goodwill), Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IntangibleAssetsGrossExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Gross carrying amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IntangibleAssetsGrossExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Intangible Assets, Gross (Excluding Goodwill) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoncashInvestingAndFinancingItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Supplemental disclosure of non-cash investing and financing activities: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoncashInvestingAndFinancingItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Noncash Investing and Financing Items [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Effect of dilutive securities, stock options, RSUs and ESPP shares </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Incremental Common Shares Attributable to Dilutive Effect of Share-Based Payment Arrangements </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Number of options, Forfeited </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PerpetualLicensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Perpetual licenses [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PerpetualLicensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Perpetual Licenses [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PerpetualLicensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Perpetual licenses. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule of Anti-dilutive shares excluded from the computation of diluted net loss per share </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Segment Information </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Segment Reporting Disclosure [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> City Area Code </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> City Area Code </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> OPERATING ACTIVITIES: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Net Cash Provided by (Used in) Operating Activities [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_NCJudgementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> N C Judgement </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_NCJudgementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> N C Judgement [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_NCJudgementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> NC judgement. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Restricted Cash and Cash Equivalents, Noncurrent, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Restricted cash included in other long-term assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Restricted Cash and Cash Equivalents, Noncurrent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_OtherProductAndServiceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_OtherProductAndServiceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Product And Service [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_OtherProductAndServiceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Other product and service. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SharesFairValueReclassificationsOfTemporaryToPermanentEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Remaining mezzanine equity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SharesFairValueReclassificationsOfTemporaryToPermanentEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Shares Fair Value Reclassifications Of Temporary To Permanent Equity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SharesFairValueReclassificationsOfTemporaryToPermanentEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Shares fair value reclassifications of temporary to permanent equity. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Less: accumulated depreciation and amortization </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> General and Administrative Expense, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> General and administrative </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> General and Administrative Expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GranteeStatusAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Grantee Status </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GranteeStatusAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Grantee Status [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Denominator for basic loss per share--weighted average shares </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Weighted Average Number of Shares Outstanding, Basic, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Weighted Average Number of Shares Outstanding, Basic </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average number of shares used in computing net loss per share, basic </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> FINANCING ACTIVITIES: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Net Cash Provided by (Used in) Financing Activities [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AccruedDefinedContributionPlanLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Defined contribution plan liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AccruedDefinedContributionPlanLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accrued Defined Contribution Plan Liabilities Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_AccruedDefinedContributionPlanLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Accrued defined contribution plan liabilities current. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Summary of Restricted Stock Units Awarded </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Statement [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Statement [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Summary of Stock Option Activity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement, Option, Activity [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Deferred revenue </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Increase (Decrease) in Contract with Customer, Liability </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ClientEngineeringServicesSegmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> CES [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ClientEngineeringServicesSegmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Client Engineering Services Segment [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ClientEngineeringServicesSegmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Client engineering services. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Document Fiscal Period Focus </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Document Fiscal Period Focus </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedProfessionalFeesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accrued professional fees </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedProfessionalFeesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accrued Professional Fees, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Statement [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Statement [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule of Convertible Notes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertibleDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Convertible Debt [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Convertible Senior Notes Due in 2024 [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Convertible Senior Notes Due In Two Thousand Twenty Four [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Convertible senior notes due in two thousand twenty four. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Stock repurchase program, Repurchase Shares </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MaintenanceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Maintenance [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MaintenanceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Maintenance [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_WorldProgrammingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> World Programming [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_WorldProgrammingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> World Programming [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_WorldProgrammingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> World Programming. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockRepurchaseProgramRepurchaseAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Stock repurchase program, Repurchase amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockRepurchaseProgramRepurchaseAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Repurchase Program, Repurchase Amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockRepurchaseProgramRepurchaseAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Stock repurchase program repurchase amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Accounts Receivable, after Allowance for Credit Loss, Current, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accounts receivable, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accounts Receivable, after Allowance for Credit Loss, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Cumulative Effect, Period of Adoption </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Cumulative Effect, Period of Adoption [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Common Stock [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Common Stock [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt Instrument [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Cash and Cash Equivalents, at Carrying Value, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Cash and cash equivalents </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Cash and Cash Equivalents, at Carrying Value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Summary of Stock-Based Compensation </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Aggregate intrinsic value, Exercisable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Common Stock, Shares Outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Common Stock, Shares Outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Antidilutive Securities, Name [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherOperatingIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Other operating (income) expense, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherOperatingIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other operating expense (income), net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherOperatingIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Operating Income (Expense), Net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareRelatedServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Software related services [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareRelatedServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Software Related Services [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SoftwareRelatedServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Software related services. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SummaryOfOtherIntangibleAssetsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Summary Of Other Intangible Assets [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SummaryOfOtherIntangibleAssetsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Summary Of Other Intangible Assets [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SummaryOfOtherIntangibleAssetsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Summary of other intangible assets. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CoverAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Cover [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Document Fiscal Year Focus </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Document Fiscal Year Focus </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingencyDamagesPaidValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Outstanding loss contingency damages paid </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingencyDamagesPaidValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Loss Contingency, Damages Paid, Value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNoteTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accumulated Other Comprehensive Loss </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNoteTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Comprehensive Income (Loss) Note [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OptionIndexedToIssuersEquityTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Option Indexed to Issuer's Equity, Type [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Income tax receivable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Income Taxes Receivable, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Segment Reporting [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Security Exchange Name </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Security Exchange Name </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other comprehensive income before reclassification </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Comprehensive Income (Loss), before Reclassifications, before Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Recent Accounting Guidance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> New Accounting Pronouncements, Policy [Policy Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Preferred stock, shares issued </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Preferred Stock, Shares Issued </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Preferred stock, shares authorized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Preferred Stock, Shares Authorized </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CustomerRelationshipsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Customer Relationships [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CustomerRelationshipsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Customer Relationships [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Total property and equipment </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Property, Plant and Equipment, Gross, Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Property, Plant and Equipment, Gross, Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Property, Plant and Equipment, Gross, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Property, Plant and Equipment, Gross </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average exercise price per share, Forfeited </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionAcquireeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Business Acquisition, Acquiree </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionAcquireeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Business Acquisition, Acquiree [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Other Comprehensive Income (Loss), Tax, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossTax_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Tax effects </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Comprehensive Income (Loss), Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average shares outstanding: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Weighted Average Number of Shares Outstanding, Diluted [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Exercise of stock options </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Issued During Period, Value, Stock Options Exercised </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Emerging Growth Company </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Emerging Growth Company </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromConvertibleDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Proceeds from Convertible Debt </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromConvertibleDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Proceeds from issuance of convertible senior notes, net of discounts and commissions </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Intrinsic value of options exercised </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period, Intrinsic Value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Amendment Flag </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Amendment Flag </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToUnderwriters_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Additional principal amount of notes to underwriters </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToUnderwriters_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Option To Purchase Additional Principal Amount Of Notes To Underwriters </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToUnderwriters_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Option to purchase additional principal amount of notes to underwriters. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Vesting of restricted stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Issued During Period, Value, Restricted Stock Award, Gross </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleTermsOfConversionFeature_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument, convertible, terms of conversion feature </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleTermsOfConversionFeature_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Convertible, Terms of Conversion Feature </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_BusinessCombinationContingentConsiderationMarkToMarketAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Business combination contingent consideration mark to market adjustments </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_BusinessCombinationContingentConsiderationMarkToMarketAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Business Combination Contingent Consideration Mark to Market Adjustments </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_BusinessCombinationContingentConsiderationMarkToMarketAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Business combination contingent consideration mark to market adjustments. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfAdoptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accounting Standards Update </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfAdoptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accounting Standards Update [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Basis of Presentation </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Basis of Accounting, Policy [Policy Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_EffectiveIncomeTaxRateReconciliationReconcilingItemsDiscreteBenefitsAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Effective income tax rate reconciliation reconciling items discrete benefits amount. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_EffectiveIncomeTaxRateReconciliationReconcilingItemsDiscreteBenefitsAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Effective Income Tax Rate Reconciliation Reconciling Items Discrete Benefits Amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_EffectiveIncomeTaxRateReconciliationReconcilingItemsDiscreteBenefitsAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Net discrete expense (benefit) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalizedContractCostNetNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Capitalized contract cost net, noncurrent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalizedContractCostNetNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Capitalized Contract Cost, Net, Noncurrent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PutRightExercisePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Put right exercise period from date of purchase </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PutRightExercisePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Put Right Exercise Period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PutRightExercisePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Put right exercise period. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity File Number </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Securities Act File Number </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Maturity date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Line of Credit Facility, Expiration Date </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerRefundLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Billings in excess of cost </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerRefundLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Contract with Customer, Refund Liability, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Goodwill and Intangible Assets Disclosure [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Total cash, cash equivalents, and restricted cash </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Cash, cash equivalents and restricted cash at beginning of year </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Cash, cash equivalents and restricted cash at end of period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwentyNineteenCreditAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Twenty Nineteen Credit Agreement </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwentyNineteenCreditAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Twenty Nineteen Credit Agreement [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_TwentyNineteenCreditAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Twenty nineteen credit agreement. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ChangeInPresentationOfCostsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Change in Presentation of Costs </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ChangeInPresentationOfCostsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Change In Presentation Of Costs [Policy Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ChangeInPresentationOfCostsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Change in presentation of costs. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SupplementaryInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Property, Plant and Equipment [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SupplementaryInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Supplementary Information [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SupplementaryInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Supplementary information. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Accounts Payable, Current, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accounts payable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accounts Payable, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt Instrument </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value, Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value, Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average grant date fair value of RSUs </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Stock Purchase Agreement [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Stock Purchase Agreement [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Stock Purchase Agreement [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_StockPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Stock purchase agreement. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Total operating expenses </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Operating Expenses </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Business acquisition, shares issued value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Business Acquisition, Equity Interest Issued or Issuable, Value Assigned </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_MaintenanceAndOtherServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Maintenance and Other Services [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_MaintenanceAndOtherServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Maintenance And Other Services [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_MaintenanceAndOtherServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Maintenance and other services. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Retirement related benefit plans (net of tax effect of $0, $0, $(79) and $7, respectively) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Retirement related benefit plans (net of tax effect of $0, $0, $(79) and $7, respectively) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel"> Retirement related benefit plans, net of tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PrincipalAmountPlusAccruedAndUnpaidInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Principal Amount Plus Accrued and Unpaid Interest </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PrincipalAmountPlusAccruedAndUnpaidInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Principal Amount Plus Accrued and Unpaid Interest </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_PrincipalAmountPlusAccruedAndUnpaidInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Principal amount plus accrued and unpaid interest. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Preferred stock ($0.0001 par value), authorized 45,000 shares, none issued and outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Preferred Stock, Value, Issued </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Small Business </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Small Business </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Shell Company </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Shell Company </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromDebtNetOfIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Net proceeds from issuance of costs </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromDebtNetOfIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Proceeds from Debt, Net of Issuance Costs </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_EmployeeStockOptionAndEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Stock Options and ESPP [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_EmployeeStockOptionAndEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Employee Stock Option And Employee Stock Purchase Plan [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_EmployeeStockOptionAndEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Employee stock option and employee stock purchase plan [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Net loss per share </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Earnings Per Share [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherSundryLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other long-term liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherSundryLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Sundry Liabilities, Noncurrent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Address, Address Line One </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Address, Address Line One </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SalesRevenueNetMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revenue Benchmark [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OptionIndexedToIssuersEquityTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Option Indexed to Issuer's Equity, Type [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Antidilutive Securities [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other accrued expenses and current liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Liabilities, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Finite-Lived Intangible Assets, Gross, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Gross carrying amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Finite-Lived Intangible Assets, Gross </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Subsequent Event Type [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Income Statement Location </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Income Statement Location [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Net Income (Loss), Including Portion Attributable to Noncontrolling Interest </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Net loss </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFrequencyOfPeriodicPayment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument frequency of periodic payment </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFrequencyOfPeriodicPayment_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Frequency of Periodic Payment </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Depreciation, Depletion and Amortization, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Depreciation and amortization </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Depreciation and amortization </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Depreciation, Depletion and Amortization </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductOrServiceAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Product and Service </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductOrServiceAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Product and Service [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Deferred revenue, non-current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Contract with Customer, Liability, Noncurrent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Title of 12(b) Security </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Title of 12(b) Security </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioPreviouslyReportedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Previously Reported [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioPreviouslyReportedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Previously Reported [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accumulated amortization </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Finite-Lived Intangible Assets, Accumulated Amortization </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> MEZZANINE EQUITY </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TemporaryEquityCarryingAmountAttributableToParent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Temporary Equity, Carrying Amount, Attributable to Parent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Reconciliation of U.S. GAAP (Loss) Income Before Income Taxes to Adjusted EBITDA </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingencyDamagesAwardedValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Loss contingency damages awarded value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingencyDamagesAwardedValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Loss Contingency, Damages Awarded, Value </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accounting Standards Update </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accounting Standards Update [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument, convertible, threshold percentage of conversion price </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Convertible, Threshold Percentage of Stock Price Trigger </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Prepaid and Other Current Assets [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Prepaid Expenses and Other Current Assets [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingChangesAndErrorCorrectionsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accounting Changes and Error Corrections [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> INVESTING ACTIVITIES: </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Net Cash Provided by (Used in) Investing Activities [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Long-Term Line of Credit, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Loan outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Long-Term Line of Credit </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ClientEngineeringServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Client Engineering Services [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ClientEngineeringServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Client Engineering Services [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ClientEngineeringServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Client engineering services. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Long-Lived Tangible Asset </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Long-Lived Tangible Asset [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Interest Expense, Debt </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average remaining contractual term (years), Exercisable </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfOtherNonoperatingIncomeExpenseTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Other Nonoperating Income (Expense) [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfOtherNonoperatingIncomeExpenseTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule of Other (income) Expense, Net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Common Stock, Shares, Outstanding, Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Common Stock, Shares, Outstanding, Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Common stock, shares outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Common Stock, Shares, Outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Stock-Based Compensation </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Payment Arrangement [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedRoyaltiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accrued royalties </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedRoyaltiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accrued Royalties, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionByUniqueDescriptionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt Conversion Description </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionByUniqueDescriptionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Conversion Description [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowElementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Supplemental Cash Flow Elements [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConcentrationRiskTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Concentration Risk Type [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Income Statement Location </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Income Statement Location [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average exercise price per share, Granted </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessCombinationAndAssetAcquisitionAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Business Combination and Asset Acquisition [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Document Type </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Document Type </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingStandardsUpdate202006Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> ASU 2020-06 [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingStandardsUpdate202006Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accounting Standards Update 2020-06 [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Credit facility </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Line of Credit Facility, Current Borrowing Capacity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Net cash used in investing activities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Net Cash Provided by (Used in) Investing Activities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Document Quarterly Report </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Document Quarterly Report </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Goodwill and Other Intangible Assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Goodwill and Intangible Assets Disclosure [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Number of RSUs, Forfeited </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ScheduleOfIncomeTaxExpenseBenefitAndEffectiveTaxRateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule of Income Tax Expense and Effective Tax Rate </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ScheduleOfIncomeTaxExpenseBenefitAndEffectiveTaxRateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule Of Income Tax Expense Benefit And Effective Tax Rate Table [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ScheduleOfIncomeTaxExpenseBenefitAndEffectiveTaxRateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Schedule Of Income Tax Expense Benefit And Effective Tax Rate [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Net Cash Provided by (Used in) Financing Activities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Net cash provided by financing activities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxesAndTaxCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Deferred Income Taxes and Tax Credits, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxesAndTaxCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Deferred Income Taxes and Tax Credits </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxesAndTaxCredits_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Deferred income taxes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Entity Filer Category </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Entity Filer Category </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCurrentLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Summary of Other Accrued Expenses and Current Liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCurrentLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Current Liabilities [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_CurrencyLossesOnAcquisitionRelatedIntercompanyLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Currency losses on acquisition-related intercompany loans </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_CurrencyLossesOnAcquisitionRelatedIntercompanyLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Currency Losses On Acquisition Related Intercompany Loans </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_CurrencyLossesOnAcquisitionRelatedIntercompanyLoans_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Currency losses on acquisition related intercompany loans. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Balance Sheet Location </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Balance Sheet Location [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_GainOnMarkToMarketAdjustmentOfContingentConsideration_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Gain on mark-to-market adjustment of contingent consideration </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_GainOnMarkToMarketAdjustmentOfContingentConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Gain on mark-to-market adjustment of contingent consideration </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_GainOnMarkToMarketAdjustmentOfContingentConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Gain On Mark To Market Adjustment Of Contingent Consideration </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_GainOnMarkToMarketAdjustmentOfContingentConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Gain on mark to market adjustment of contingent consideration. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Other long-term assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Increase (Decrease) in Other Noncurrent Assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SummaryOfOtherIntangibleAssetsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Summary Of Other Intangible Assets [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SummaryOfOtherIntangibleAssetsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Summary Of Other Intangible Assets [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SummaryOfOtherIntangibleAssetsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Summary Of Other Intangible Assets [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Foreign currency translation, net of tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Foreign currency translation (net of tax effect of $0 for all periods) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SecuredCreditAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Secured Credit Agreement [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SecuredCreditAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Secured Credit Agreement [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SecuredCreditAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Description should be secured credit agreement. And custom label should be credit agreement. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentConvertibleConversionRatePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument conversion rate principal amount of notes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentConvertibleConversionRatePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument Convertible Conversion Rate Principal Amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentConvertibleConversionRatePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Debt instrument convertible conversion rate principal amount. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TradeNamesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Trade Names [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TradeNamesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Trade Names [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other (income) expense, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Other (income) expense, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Nonoperating Income (Expense), Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel"> Other expense, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Nonoperating Income (Expense) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalExpendituresIncurredButNotYetPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Property and equipment in accounts payable and other current liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalExpendituresIncurredButNotYetPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Capital Expenditures Incurred but Not yet Paid </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> TOTAL LIABILITIES </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule Of Property Plant And Equipment [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Property, Plant and Equipment [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SpecialAdjustmentsInterestIncomeAndOther_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Special adjustments interest income and other. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SpecialAdjustmentsInterestIncomeAndOther_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Special Adjustments Interest Income And Other </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_SpecialAdjustmentsInterestIncomeAndOther_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Special adjustments, interest income and other </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accumulated Other Comprehensive Income Loss [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Accumulated Other Comprehensive Income (Loss) [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentPrincipalOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument principal outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentPrincipalOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument Principal Outstanding </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_DebtInstrumentPrincipalOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Debt instrument principal outstanding. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> TOTAL STOCKHOLDERS’ EQUITY </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Beginning balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Ending balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Equity, Attributable to Parent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted-average useful life of acquired finite-lived intangible assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Acquired Finite-Lived Intangible Assets, Weighted Average Useful Life </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProductConcentrationRiskMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Product Concentration Risk [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IntangibleAssetsNetExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Net carrying amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IntangibleAssetsNetExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Other intangible assets, net </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IntangibleAssetsNetExcludingGoodwill_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Intangible Assets, Net (Excluding Goodwill) </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule of Changes Made to the Consolidated Statement of Income </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Error Corrections and Prior Period Adjustments [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Net loss </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel"> Net loss </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Interest Expense, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Interest expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Interest expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Interest Expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfConvertibleDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Repayments of Convertible Debt </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfConvertibleDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Repurchase of convertible senior notes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Contract with Customer, Asset, after Allowance for Credit Loss, Current, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Contract assets </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Contract with Customer, Asset, after Allowance for Credit Loss, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Statement of Financial Position [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Denominator for dilutive loss per share </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Weighted Average Number of Shares Outstanding, Diluted </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Weighted average number of shares used in computing net loss per share, diluted </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Effective Income Tax Rate Reconciliation, Percent, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Effective tax rate </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EffectiveIncomeTaxRateContinuingOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Effective Income Tax Rate Reconciliation, Percent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentRepurchasedFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Debt instrument repurchased face amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentRepurchasedFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Repurchased Face Amount </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_InterestIncomeAndOther_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Special adjustments, interest income and other </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_InterestIncomeAndOther_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Interest Income And Other </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_InterestIncomeAndOther_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Interest income and other. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_InterestIncomeAndOther_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Interest income </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoncashOrPartNoncashAcquisitionsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Noncash or Part Noncash Acquisitions [Table] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentRedemptionPricePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Debt Instrument, Redemption Price, Percentage </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Percentage of purchase price for each share of common stock purchased of lower of fair market value per share on first day of applicable offering period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Purchase Price of Common Stock, Percent </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Use of Estimates </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Use of Estimates, Policy [Policy Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Income Taxes </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Income Tax Disclosure [Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndOtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Interest income </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndOtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Interest and Other Income </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndOtherIncome_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Interest income </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel"> Weighted average exercise price per share, Outstanding, Beginning Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel"> Weighted average exercise price per share, Outstanding, Ending Balance </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Schedule Of Computation of Numerators and Denominators Used in Basic and Diluted Net loss Per Share Amounts </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Convertible Notes, Holders Conversion Rights, Circumstances 1 [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Convertible Notes Holders Conversion Rights Under Circumstances One [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Convertible notes, holders conversion rights under circumstances 1. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseDebtExcludingAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Contractual interest expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseDebtExcludingAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Interest Expense, Debt, Excluding Amortization </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Disaggregation Of Revenue [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Disaggregation of Revenue [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Leasehold Improvements [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Leasehold Improvements [Member] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_BusinessCombinationEstimatedPostCombinationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Business combination, estimated post combination expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_BusinessCombinationEstimatedPostCombinationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Business Combination Estimated Post Combination Expense </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_BusinessCombinationEstimatedPostCombinationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Business combination estimated post combination expense. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_CashPaidForRepurchaseAndRetirementOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Cash paid for repurchase and retirement of common stock. </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_CashPaidForRepurchaseAndRetirementOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Cash Paid For Repurchase And Retirement Of Common Stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_CashPaidForRepurchaseAndRetirementOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Payments for repurchase and retirement of common stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_CashPaidForRepurchaseAndRetirementOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Payments for repurchase and retirement of common stock </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Fair Value Disclosures [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReclassificationsOfTemporaryToPermanentEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Reclassification of mezzanine equity to permanent equity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ReclassificationsOfTemporaryToPermanentEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Reclassifications of Temporary to Permanent Equity </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Payments to Acquire Property, Plant, and Equipment, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Capital expenditures </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Payments to Acquire Property, Plant, and Equipment </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RestatementDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Revision of Prior Period [Domain] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel"> Number of RSUs, Vested </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel"> Employee-related Liabilities, Current, Total </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Accrued compensation and benefits </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Employee-related Liabilities, Current </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Business Acquisition </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BusinessAcquisitionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Business Acquisition [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Income Tax Disclosure [Abstract] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Finite-Lived Intangible Assets by Major Class </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Finite-Lived Intangible Assets by Major Class [Axis] </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_EmployeeStockPurchasePlanLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel"> Employee stock purchase plan obligations </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_EmployeeStockPurchasePlanLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label"> Employee Stock Purchase Plan Liabilities </link:label>
<link:label xml:lang="en-US" xlink:type="resource" xlink:label="altr_EmployeeStockPurchasePlanLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation"> Employee stock purchase plan liabilities. </link:label>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentTransitionReport" xlink:to="dei_DocumentTransitionReport_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueRemainingPerformanceObligation" xlink:to="us-gaap_RevenueRemainingPerformanceObligation_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestOnConvertibleDebtNetOfTax" xlink:to="us-gaap_InterestOnConvertibleDebtNetOfTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_GoodwillAffectOfForeignCurrencyTranslationGainLossAndOther" xlink:to="altr_GoodwillAffectOfForeignCurrencyTranslationGainLossAndOther_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherLiabilitiesNoncurrent" xlink:to="us-gaap_OtherLiabilitiesNoncurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:to="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedStockUnitsRSUMember" xlink:to="us-gaap_RestrictedStockUnitsRSUMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_AccruedObligationsForAcquisitionOfBusinesses" xlink:to="altr_AccruedObligationsForAcquisitionOfBusinesses_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SoftwareRelatedServiceMember" xlink:to="altr_SoftwareRelatedServiceMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueDisclosuresTextBlock" xlink:to="us-gaap_FairValueDisclosuresTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:to="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_AccountsReceivableNetCurrentMember" xlink:to="altr_AccountsReceivableNetCurrentMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ComputerEquipmentAndSoftwareMember" xlink:to="altr_ComputerEquipmentAndSoftwareMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisaggregationOfRevenueTableTextBlock" xlink:to="us-gaap_DisaggregationOfRevenueTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" xlink:to="us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskByTypeAxis" xlink:to="us-gaap_ConcentrationRiskByTypeAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerLiabilityCurrent" xlink:to="us-gaap_ContractWithCustomerLiabilityCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock" xlink:to="us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_PaymentsForRepurchaseOfCommonStockShares" xlink:to="altr_PaymentsForRepurchaseOfCommonStockShares_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DepositLiabilitiesAccruedInterest" xlink:to="us-gaap_DepositLiabilitiesAccruedInterest_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConvertibleDebtFairValueDisclosures" xlink:to="us-gaap_ConvertibleDebtFairValueDisclosures_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GoodwillAcquiredDuringPeriod" xlink:to="us-gaap_GoodwillAcquiredDuringPeriod_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquitySharesIssued" xlink:to="us-gaap_TemporaryEquitySharesIssued_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NoncashOrPartNoncashAcquisitionsLineItems" xlink:to="us-gaap_NoncashOrPartNoncashAcquisitionsLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:to="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_TwoThousandTwentyThreeAcquisitionsMember" xlink:to="altr_TwoThousandTwentyThreeAcquisitionsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BalanceSheetLocationAxis" xlink:to="us-gaap_BalanceSheetLocationAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsCurrent" xlink:to="us-gaap_AssetsCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressStateOrProvince" xlink:to="dei_EntityAddressStateOrProvince_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_LitigationCaseTypeDomain" xlink:to="srt_LitigationCaseTypeDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredIncomeTaxAssetsNet" xlink:to="us-gaap_DeferredIncomeTaxAssetsNet_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_TermLicensesAndOtherMember" xlink:to="altr_TermLicensesAndOtherMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComprehensiveIncomeNetOfTax" xlink:to="us-gaap_ComprehensiveIncomeNetOfTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_StockIssuedDuringPeriodSharesPrivatePlacementNewIssues" xlink:to="altr_StockIssuedDuringPeriodSharesPrivatePlacementNewIssues_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_TradingSymbol" xlink:to="dei_TradingSymbol_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesIssued" xlink:to="us-gaap_CommonStockSharesIssued_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock" xlink:to="us-gaap_ScheduleOfRestrictedCashAndCashEquivalentsTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock" xlink:to="us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_DocumentAndEntityInformationTable" xlink:to="altr_DocumentAndEntityInformationTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:to="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLossAbstract" xlink:to="us-gaap_NetIncomeLossAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SellingAndMarketingExpenseMember" xlink:to="us-gaap_SellingAndMarketingExpenseMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharesOutstanding" xlink:to="us-gaap_SharesOutstanding_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:to="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:to="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BusinessCombinationDisclosureTextBlock" xlink:to="us-gaap_BusinessCombinationDisclosureTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressCityOrTown" xlink:to="dei_EntityAddressCityOrTown_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesTwoMember" xlink:to="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesTwoMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_StockRepurchaseProgramAveragePricePerShare" xlink:to="altr_StockRepurchaseProgramAveragePricePerShare_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtDisclosureTextBlock" xlink:to="us-gaap_DebtDisclosureTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:to="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventMember" xlink:to="us-gaap_SubsequentEventMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_RightOfUseAssetsUnderFinanceLeasesMember" xlink:to="altr_RightOfUseAssetsUnderFinanceLeasesMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalMember" xlink:to="us-gaap_AdditionalPaidInCapitalMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_LiabilitiesCurrentAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_AssetsCurrentAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockParOrStatedValuePerShare" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax" xlink:to="us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfStockholdersEquityAbstract" xlink:to="us-gaap_StatementOfStockholdersEquityAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityCurrent" xlink:to="us-gaap_OperatingLeaseLiabilityCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentMaturityDate" xlink:to="us-gaap_DebtInstrumentMaturityDate_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentNet" xlink:to="us-gaap_PropertyPlantAndEquipmentNet_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_PromissoryNotesIssuedAndDeferredPaymentObligationsForAcquisitions" xlink:to="altr_PromissoryNotesIssuedAndDeferredPaymentObligationsForAcquisitions_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_ClassOfStockDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestructuringCharges" xlink:to="us-gaap_RestructuringCharges_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_PaymentForRepurchaseOfCommonStockShares" xlink:to="altr_PaymentForRepurchaseOfCommonStockShares_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BusinessCombinationContingentConsiderationLiability" xlink:to="us-gaap_BusinessCombinationContingentConsiderationLiability_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract" xlink:to="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_TypeOfArrangementAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCentralIndexKey" xlink:to="dei_EntityCentralIndexKey_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherIntangibleAssetsMember" xlink:to="us-gaap_OtherIntangibleAssetsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameDomain" xlink:to="us-gaap_PlanNameDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherLiabilitiesDisclosureAbstract" xlink:to="us-gaap_OtherLiabilitiesDisclosureAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_TwoThousandAndSeventeenEquityIncentivePlanMember" xlink:to="altr_TwoThousandAndSeventeenEquityIncentivePlanMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SalesCommissionsAndFees" xlink:to="us-gaap_SalesCommissionsAndFees_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesOutstanding" xlink:to="us-gaap_PreferredStockSharesOutstanding_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" xlink:to="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfGoodwillTextBlock" xlink:to="us-gaap_ScheduleOfGoodwillTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrent" xlink:to="us-gaap_LiabilitiesCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityTaxIdentificationNumber" xlink:to="dei_EntityTaxIdentificationNumber_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:to="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsOfDebtIssuanceCosts" xlink:to="us-gaap_PaymentsOfDebtIssuanceCosts_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ConceptEngineeringMember" xlink:to="altr_ConceptEngineeringMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAdditionalDisclosuresAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingDilutedDisclosureItemsAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ProfessionalSoftwareServicesMember" xlink:to="altr_ProfessionalSoftwareServicesMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourAndTwoThousandTwentySevenMember" xlink:to="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourAndTwoThousandTwentySevenMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan" xlink:to="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameAxis" xlink:to="us-gaap_PlanNameAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Assets" xlink:to="us-gaap_Assets_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_RevenueFromContractsWithCustomersLineItems" xlink:to="altr_RevenueFromContractsWithCustomersLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseRightOfUseAsset" xlink:to="us-gaap_OperatingLeaseRightOfUseAsset_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonClassAMember" xlink:to="us-gaap_CommonClassAMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityRegistrantName" xlink:to="dei_EntityRegistrantName_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredFinanceCostsNet" xlink:to="us-gaap_DeferredFinanceCostsNet_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SoftwareMember" xlink:to="altr_SoftwareMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsAccumulatedDeficit" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="us-gaap_SupplementalCashFlowInformationAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_NumberOfPriorBusinessAcquistionsValuationFinalized" xlink:to="altr_NumberOfPriorBusinessAcquistionsValuationFinalized_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsMember" xlink:to="us-gaap_RetainedEarningsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_StatementClassOfStockAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredIncomeTaxLiabilitiesNet" xlink:to="us-gaap_DeferredIncomeTaxLiabilitiesNet_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:to="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MinimumMember" xlink:to="srt_MinimumMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromStockOptionsExercised" xlink:to="us-gaap_ProceedsFromStockOptionsExercised_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SignificantAccountingPoliciesTextBlock" xlink:to="us-gaap_SignificantAccountingPoliciesTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedIncomeTaxesCurrent" xlink:to="us-gaap_AccruedIncomeTaxesCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_EquityComponentDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_StatementBusinessSegmentsAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConversionOfStockSharesConverted1" xlink:to="us-gaap_ConversionOfStockSharesConverted1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LandMember" xlink:to="us-gaap_LandMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonstock" xlink:to="altr_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonstock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AmortizationOfFinancingCostsAndDiscounts" xlink:to="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:to="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_FurnitureEquipmentAndOtherMember" xlink:to="altr_FurnitureEquipmentAndOtherMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="us-gaap_DebtDisclosureAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BuildingAndBuildingImprovementsMember" xlink:to="us-gaap_BuildingAndBuildingImprovementsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_AmountWithheldOnBehalfOfEmployeesForFuturePurchase" xlink:to="altr_AmountWithheldOnBehalfOfEmployeesForFuturePurchase_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCurrentReportingStatus" xlink:to="dei_EntityCurrentReportingStatus_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromPaymentsForOtherFinancingActivities" xlink:to="us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesAuthorized" xlink:to="us-gaap_CommonStockSharesAuthorized_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PutOptionMember" xlink:to="us-gaap_PutOptionMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_TwoThousandAndTwentyOneEmployeeStockPurchasePlanMember" xlink:to="altr_TwoThousandAndTwentyOneEmployeeStockPurchasePlanMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpense" xlink:to="us-gaap_ResearchAndDevelopmentExpense_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueByBalanceSheetGroupingTable" xlink:to="us-gaap_FairValueByBalanceSheetGroupingTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_RevenueFromContractsWithCustomersTable" xlink:to="altr_RevenueFromContractsWithCustomersTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:to="us-gaap_StockRepurchaseProgramAuthorizedAmount1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AmortizationOfIntangibleAssets" xlink:to="us-gaap_AmortizationOfIntangibleAssets_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockValue" xlink:to="us-gaap_CommonStockValue_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:to="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherNoncashIncomeExpense" xlink:to="us-gaap_OtherNoncashIncomeExpense_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ConvertibleSeniorNotesDueInTwoThousandTwentySevenMember" xlink:to="altr_ConvertibleSeniorNotesDueInTwoThousandTwentySevenMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:to="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CurrentFiscalYearEndDate" xlink:to="dei_CurrentFiscalYearEndDate_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensation" xlink:to="us-gaap_ShareBasedCompensation_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_StockPurchaseProgramSharesAcquired" xlink:to="altr_StockPurchaseProgramSharesAcquired_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingIncomeLoss" xlink:to="us-gaap_OperatingIncomeLoss_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued" xlink:to="us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="us-gaap_IncomeTaxExpenseBenefit_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpenseMember" xlink:to="us-gaap_ResearchAndDevelopmentExpenseMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConvertibleLongTermNotesPayable" xlink:to="us-gaap_ConvertibleLongTermNotesPayable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NatureOfOperations" xlink:to="us-gaap_NatureOfOperations_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesAcquisitions" xlink:to="us-gaap_StockIssuedDuringPeriodSharesAcquisitions_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskPercentage1" xlink:to="us-gaap_ConcentrationRiskPercentage1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AllocatedShareBasedCompensationExpense" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ProceedsFromEmployeeStockPurchasePlanContributions" xlink:to="altr_ProceedsFromEmployeeStockPurchasePlanContributions_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisaggregationOfRevenueTable" xlink:to="us-gaap_DisaggregationOfRevenueTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLossAttributableToParentDiluted" xlink:to="us-gaap_NetIncomeLossAttributableToParentDiluted_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsNet_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock" xlink:to="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxesPaid" xlink:to="us-gaap_IncomeTaxesPaid_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueFromContractWithCustomerTextBlock" xlink:to="us-gaap_RevenueFromContractWithCustomerTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:to="us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LicenseMember" xlink:to="us-gaap_LicenseMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentFaceAmount" xlink:to="us-gaap_DebtInstrumentFaceAmount_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToInitialPurchaser" xlink:to="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToInitialPurchaser_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember" xlink:to="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_LineOfCreditFacilityIncreaseInBorrowingCapacity" xlink:to="altr_LineOfCreditFacilityIncreaseInBorrowingCapacity_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OperatingExpensesAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentAbstract" xlink:to="us-gaap_PropertyPlantAndEquipmentAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SettlementOfConvertibleSeniorNotes" xlink:to="altr_SettlementOfConvertibleSeniorNotes_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_FairValueExpenseRecognized" xlink:to="altr_FairValueExpenseRecognized_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:to="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAssetsNoncurrent" xlink:to="us-gaap_OtherAssetsNoncurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentConvertibleIfConvertedValueInExcessOfPrincipal" xlink:to="us-gaap_DebtInstrumentConvertibleIfConvertedValueInExcessOfPrincipal_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Depreciation" xlink:to="us-gaap_Depreciation_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestPaidNet" xlink:to="us-gaap_InterestPaidNet_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonClassBMember" xlink:to="us-gaap_CommonClassBMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_DebtInstrumentConvertibleThresholdBusinessDays" xlink:to="altr_DebtInstrumentConvertibleThresholdBusinessDays_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_StockholdersEquityAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_DocumentAndEntityInformationLineItems" xlink:to="altr_DocumentAndEntityInformationLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DevelopedTechnologyRightsMember" xlink:to="us-gaap_DevelopedTechnologyRightsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueRemainingPerformanceObligationPercentage" xlink:to="us-gaap_RevenueRemainingPerformanceObligationPercentage_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CostOfGoodsAndServicesSold" xlink:to="us-gaap_CostOfGoodsAndServicesSold_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization" xlink:to="altr_AdjustedEarningsBeforeInterestTaxesDepreciationAndAmortization_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ScheduleOfOtherIntangibleAssetsTableTextBlock" xlink:to="altr_ScheduleOfOtherIntangibleAssetsTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareAbstract" xlink:to="us-gaap_EarningsPerShareAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ExpenseOnRepurchaseOfConvertibleSeniorNote" xlink:to="altr_ExpenseOnRepurchaseOfConvertibleSeniorNote_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LossContingenciesTable" xlink:to="us-gaap_LossContingenciesTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_LitigationCaseAxis" xlink:to="srt_LitigationCaseAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SegmentDomain" xlink:to="us-gaap_SegmentDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LicenseAndServiceMember" xlink:to="us-gaap_LicenseAndServiceMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherNoncurrentAssetsMember" xlink:to="us-gaap_OtherNoncurrentAssetsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SoftwareSegmentMember" xlink:to="altr_SoftwareSegmentMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareBasic" xlink:to="us-gaap_EarningsPerShareBasic_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ConvertibleSharesMember" xlink:to="altr_ConvertibleSharesMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock" xlink:to="us-gaap_ScheduleOfAccumulatedOtherComprehensiveIncomeLossTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingencies" xlink:to="us-gaap_CommitmentsAndContingencies_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_IncomeStatementAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CapitalizedContractCostNetCurrent" xlink:to="us-gaap_CapitalizedContractCostNetCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeMember" xlink:to="srt_RangeMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="us-gaap_LossContingenciesLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentPeriodEndDate" xlink:to="dei_DocumentPeriodEndDate_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeAxis" xlink:to="srt_RangeAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtConversionNameDomain" xlink:to="us-gaap_DebtConversionNameDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:to="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareDiluted" xlink:to="us-gaap_EarningsPerShareDiluted_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ProductsAndServicesDomain" xlink:to="srt_ProductsAndServicesDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_CurrencyGainsOnAcquisitionRelatedIntercompanyLoans" xlink:to="altr_CurrencyGainsOnAcquisitionRelatedIntercompanyLoans_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CostOfSalesMember" xlink:to="us-gaap_CostOfSalesMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskBenchmarkDomain" xlink:to="us-gaap_ConcentrationRiskBenchmarkDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardRequisiteServicePeriod1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueFromContractWithCustomerAbstract" xlink:to="us-gaap_RevenueFromContractWithCustomerAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="us-gaap_DebtInstrumentNameDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SupplementaryInformationTextBlock" xlink:to="altr_SupplementaryInformationTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_StockIssuedDuringPeriodValuePrivatePlacementNewIssues" xlink:to="altr_StockIssuedDuringPeriodValuePrivatePlacementNewIssues_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentDescription" xlink:to="us-gaap_DebtInstrumentDescription_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NumberOfReportableSegments" xlink:to="us-gaap_NumberOfReportableSegments_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember" xlink:to="us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalCommonStock" xlink:to="us-gaap_AdditionalPaidInCapitalCommonStock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SalesAndExciseTaxPayableCurrentAndNoncurrent" xlink:to="us-gaap_SalesAndExciseTaxPayableCurrentAndNoncurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsForRepurchaseOfCommonStock" xlink:to="us-gaap_PaymentsForRepurchaseOfCommonStock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent" xlink:to="us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_NumberOfEqualVestingInstallments" xlink:to="altr_NumberOfEqualVestingInstallments_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_LossOnMarkToMarketAdjustmentOfContingentConsideration" xlink:to="altr_LossOnMarkToMarketAdjustmentOfContingentConsideration_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LicenseAndMaintenanceMember" xlink:to="us-gaap_LicenseAndMaintenanceMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherNoncurrentLiabilitiesTableTextBlock" xlink:to="us-gaap_OtherNoncurrentLiabilitiesTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueAcquisitions" xlink:to="us-gaap_StockIssuedDuringPeriodValueAcquisitions_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressPostalZipCode" xlink:to="dei_EntityAddressPostalZipCode_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityInteractiveDataCurrent" xlink:to="dei_EntityInteractiveDataCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SellingAndMarketingExpense" xlink:to="us-gaap_SellingAndMarketingExpense_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_TwoThousandTwentyOneAcquisitionsMember" xlink:to="altr_TwoThousandTwentyOneAcquisitionsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GranteeStatusDomain" xlink:to="us-gaap_GranteeStatusDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1" xlink:to="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccountsPayable" xlink:to="us-gaap_IncreaseDecreaseInAccountsPayable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities" xlink:to="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RestatementAdjustmentMember" xlink:to="srt_RestatementAdjustmentMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_EquityAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShortTermDebtTable" xlink:to="us-gaap_ScheduleOfShortTermDebtTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_TheTimingOfPayrollDeductionsMember" xlink:to="altr_TheTimingOfPayrollDeductionsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RestatementAxis" xlink:to="srt_RestatementAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityIncorporationStateCountryCode" xlink:to="dei_EntityIncorporationStateCountryCode_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_StatementEquityComponentsAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:to="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent" xlink:to="us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:to="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AllOtherSegmentsMember" xlink:to="us-gaap_AllOtherSegmentsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_DebtInstrumentConvertibleThresholdMaximumPercentageOfProductOfLastReportedSalePriceOfCommonStock" xlink:to="altr_DebtInstrumentConvertibleThresholdMaximumPercentageOfProductOfLastReportedSalePriceOfCommonStock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock" xlink:to="us-gaap_NewAccountingPronouncementsAndChangesInAccountingPrinciplesTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_LocalPhoneNumber" xlink:to="dei_LocalPhoneNumber_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_PropertyPlantAndEquipmentLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtConversionConvertedInstrumentSharesIssued1" xlink:to="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures" xlink:to="us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Goodwill" xlink:to="us-gaap_Goodwill_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfNotesPayable" xlink:to="us-gaap_RepaymentsOfNotesPayable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_StatementOfCashFlowsAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquityRedemptionPricePerShare" xlink:to="us-gaap_TemporaryEquityRedemptionPricePerShare_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" xlink:to="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:to="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_SegmentReportingInformationLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GrossProfit" xlink:to="us-gaap_GrossProfit_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedTranslationAdjustmentMember" xlink:to="us-gaap_AccumulatedTranslationAdjustmentMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:to="us-gaap_ConcentrationRiskByBenchmarkAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockParOrStatedValuePerShare" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CumulativeEffectPeriodOfAdoptionAxis" xlink:to="srt_CumulativeEffectPeriodOfAdoptionAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:to="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_PowersimIncMember" xlink:to="altr_PowersimIncMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConvertibleNotesPayableCurrent" xlink:to="us-gaap_ConvertibleNotesPayableCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MaximumMember" xlink:to="srt_MaximumMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_DebtInstrumentCommencementOfInterestDate" xlink:to="altr_DebtInstrumentCommencementOfInterestDate_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentConvertibleThresholdTradingDays" xlink:to="us-gaap_DebtInstrumentConvertibleThresholdTradingDays_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles" xlink:to="us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationAggregateDisclosuresAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsForProceedsFromOtherInvestingActivities" xlink:to="us-gaap_PaymentsForProceedsFromOtherInvestingActivities_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherSundryLiabilitiesCurrent" xlink:to="us-gaap_OtherSundryLiabilitiesCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GeneralAndAdministrativeExpenseMember" xlink:to="us-gaap_GeneralAndAdministrativeExpenseMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IntangibleAssetsGrossExcludingGoodwill" xlink:to="us-gaap_IntangibleAssetsGrossExcludingGoodwill_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="us-gaap_NoncashInvestingAndFinancingItemsAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements" xlink:to="us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_PerpetualLicensesMember" xlink:to="altr_PerpetualLicensesMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock" xlink:to="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SegmentReportingDisclosureTextBlock" xlink:to="us-gaap_SegmentReportingDisclosureTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CityAreaCode" xlink:to="dei_CityAreaCode_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_NCJudgementMember" xlink:to="altr_NCJudgementMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_OtherProductAndServiceMember" xlink:to="altr_OtherProductAndServiceMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SharesFairValueReclassificationsOfTemporaryToPermanentEquity" xlink:to="altr_SharesFairValueReclassificationsOfTemporaryToPermanentEquity_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:to="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GeneralAndAdministrativeExpense" xlink:to="us-gaap_GeneralAndAdministrativeExpense_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GranteeStatusAxis" xlink:to="us-gaap_GranteeStatusAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_AccruedDefinedContributionPlanLiabilitiesCurrent" xlink:to="altr_AccruedDefinedContributionPlanLiabilitiesCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:to="us-gaap_IncreaseDecreaseInContractWithCustomerLiability_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ClientEngineeringServicesSegmentMember" xlink:to="altr_ClientEngineeringServicesSegmentMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentFiscalPeriodFocus" xlink:to="dei_DocumentFiscalPeriodFocus_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedProfessionalFeesCurrent" xlink:to="us-gaap_AccruedProfessionalFeesCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConvertibleDebtTableTextBlock" xlink:to="us-gaap_ConvertibleDebtTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourMember" xlink:to="altr_ConvertibleSeniorNotesDueInTwoThousandTwentyFourMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased" xlink:to="us-gaap_StockRepurchaseProgramRemainingNumberOfSharesAuthorizedToBeRepurchased_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MaintenanceMember" xlink:to="us-gaap_MaintenanceMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_WorldProgrammingMember" xlink:to="altr_WorldProgrammingMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_StockRepurchaseProgramRepurchaseAmount" xlink:to="altr_StockRepurchaseProgramRepurchaseAmount_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsReceivableNetCurrent" xlink:to="us-gaap_AccountsReceivableNetCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CumulativeEffectPeriodOfAdoptionDomain" xlink:to="srt_CumulativeEffectPeriodOfAdoptionDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockMember" xlink:to="us-gaap_CommonStockMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCommonStockSharesOutstanding" xlink:to="dei_EntityCommonStockSharesOutstanding_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="us-gaap_AntidilutiveSecuritiesNameDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherOperatingIncomeExpenseNet" xlink:to="us-gaap_OtherOperatingIncomeExpenseNet_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SoftwareRelatedServicesMember" xlink:to="altr_SoftwareRelatedServicesMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SummaryOfOtherIntangibleAssetsLineItems" xlink:to="altr_SummaryOfOtherIntangibleAssetsLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CoverAbstract" xlink:to="dei_CoverAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentFiscalYearFocus" xlink:to="dei_DocumentFiscalYearFocus_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LossContingencyDamagesPaidValue" xlink:to="us-gaap_LossContingencyDamagesPaidValue_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComprehensiveIncomeNoteTextBlock" xlink:to="us-gaap_ComprehensiveIncomeNoteTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OptionIndexedToIssuersEquityTypeDomain" xlink:to="us-gaap_OptionIndexedToIssuersEquityTypeDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAbstract" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTaxAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxesReceivable" xlink:to="us-gaap_IncomeTaxesReceivable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SegmentReportingAbstract" xlink:to="us-gaap_SegmentReportingAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_SecurityExchangeName" xlink:to="dei_SecurityExchangeName_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:to="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesIssued" xlink:to="us-gaap_PreferredStockSharesIssued_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesAuthorized" xlink:to="us-gaap_PreferredStockSharesAuthorized_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CustomerRelationshipsMember" xlink:to="us-gaap_CustomerRelationshipsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentGross" xlink:to="us-gaap_PropertyPlantAndEquipmentGross_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BusinessAcquisitionAcquireeDomain" xlink:to="us-gaap_BusinessAcquisitionAcquireeDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:to="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityEmergingGrowthCompany" xlink:to="dei_EntityEmergingGrowthCompany_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromConvertibleDebt" xlink:to="us-gaap_ProceedsFromConvertibleDebt_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_AmendmentFlag" xlink:to="dei_AmendmentFlag_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToUnderwriters" xlink:to="altr_OptionToPurchaseAdditionalPrincipalAmountOfNotesToUnderwriters_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross" xlink:to="us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentConvertibleTermsOfConversionFeature" xlink:to="us-gaap_DebtInstrumentConvertibleTermsOfConversionFeature_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_BusinessCombinationContingentConsiderationMarkToMarketAdjustments" xlink:to="altr_BusinessCombinationContingentConsiderationMarkToMarketAdjustments_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TypeOfAdoptionMember" xlink:to="us-gaap_TypeOfAdoptionMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:to="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_EffectiveIncomeTaxRateReconciliationReconcilingItemsDiscreteBenefitsAmount" xlink:to="altr_EffectiveIncomeTaxRateReconciliationReconcilingItemsDiscreteBenefitsAmount_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CapitalizedContractCostNetNoncurrent" xlink:to="us-gaap_CapitalizedContractCostNetNoncurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_PutRightExercisePeriod" xlink:to="altr_PutRightExercisePeriod_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityFileNumber" xlink:to="dei_EntityFileNumber_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityExpirationDate1" xlink:to="us-gaap_LineOfCreditFacilityExpirationDate1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerRefundLiabilityCurrent" xlink:to="us-gaap_ContractWithCustomerRefundLiabilityCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract" xlink:to="us-gaap_GoodwillAndIntangibleAssetsDisclosureAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract" xlink:to="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_TwentyNineteenCreditAgreementMember" xlink:to="altr_TwentyNineteenCreditAgreementMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ChangeInPresentationOfCostsPolicyTextBlock" xlink:to="altr_ChangeInPresentationOfCostsPolicyTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SupplementaryInformationAbstract" xlink:to="altr_SupplementaryInformationAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsPayableCurrent" xlink:to="us-gaap_AccountsPayableCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_StockPurchaseAgreementMember" xlink:to="altr_StockPurchaseAgreementMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_OperatingExpenses_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned" xlink:to="us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_MaintenanceAndOtherServicesMember" xlink:to="altr_MaintenanceAndOtherServicesMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_PrincipalAmountPlusAccruedAndUnpaidInterest" xlink:to="altr_PrincipalAmountPlusAccruedAndUnpaidInterest_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockValue" xlink:to="us-gaap_PreferredStockValue_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntitySmallBusiness" xlink:to="dei_EntitySmallBusiness_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityShellCompany" xlink:to="dei_EntityShellCompany_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromDebtNetOfIssuanceCosts" xlink:to="us-gaap_ProceedsFromDebtNetOfIssuanceCosts_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_EmployeeStockOptionAndEmployeeStockPurchasePlanMember" xlink:to="altr_EmployeeStockOptionAndEmployeeStockPurchasePlanMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareTextBlock" xlink:to="us-gaap_EarningsPerShareTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherSundryLiabilitiesNoncurrent" xlink:to="us-gaap_OtherSundryLiabilitiesNoncurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressAddressLine1" xlink:to="dei_EntityAddressAddressLine1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SalesRevenueNetMember" xlink:to="us-gaap_SalesRevenueNetMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OptionIndexedToIssuersEquityTypeAxis" xlink:to="us-gaap_OptionIndexedToIssuersEquityTypeAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherLiabilitiesCurrent" xlink:to="us-gaap_OtherLiabilitiesCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsGross" xlink:to="us-gaap_FiniteLivedIntangibleAssetsGross_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventTypeDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_ProfitLoss_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentFrequencyOfPeriodicPayment" xlink:to="us-gaap_DebtInstrumentFrequencyOfPeriodicPayment_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DepreciationDepletionAndAmortization" xlink:to="us-gaap_DepreciationDepletionAndAmortization_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ProductOrServiceAxis" xlink:to="srt_ProductOrServiceAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerLiabilityNoncurrent" xlink:to="us-gaap_ContractWithCustomerLiabilityNoncurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_Security12bTitle" xlink:to="dei_Security12bTitle_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ScenarioPreviouslyReportedMember" xlink:to="srt_ScenarioPreviouslyReportedMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TemporaryEquityCarryingAmountAttributableToParent" xlink:to="us-gaap_TemporaryEquityCarryingAmountAttributableToParent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTextBlock" xlink:to="us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LossContingencyDamagesAwardedValue" xlink:to="us-gaap_LossContingencyDamagesAwardedValue_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger" xlink:to="us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember" xlink:to="us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountingChangesAndErrorCorrectionsAbstract" xlink:to="us-gaap_AccountingChangesAndErrorCorrectionsAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCredit" xlink:to="us-gaap_LineOfCredit_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ClientEngineeringServicesMember" xlink:to="altr_ClientEngineeringServicesMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpenseDebt" xlink:to="us-gaap_InterestExpenseDebt_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfOtherNonoperatingIncomeExpenseTableTextBlock" xlink:to="us-gaap_ScheduleOfOtherNonoperatingIncomeExpenseTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesOutstanding" xlink:to="us-gaap_CommonStockSharesOutstanding_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock" xlink:to="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedRoyaltiesCurrent" xlink:to="us-gaap_AccruedRoyaltiesCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtConversionByUniqueDescriptionAxis" xlink:to="us-gaap_DebtConversionByUniqueDescriptionAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SupplementalCashFlowElementsAbstract" xlink:to="us-gaap_SupplementalCashFlowElementsAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConcentrationRiskTypeDomain" xlink:to="us-gaap_ConcentrationRiskTypeDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_IncomeStatementLocationDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BusinessCombinationAndAssetAcquisitionAbstract" xlink:to="us-gaap_BusinessCombinationAndAssetAcquisitionAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentType" xlink:to="dei_DocumentType_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountingStandardsUpdate202006Member" xlink:to="us-gaap_AccountingStandardsUpdate202006Member_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity" xlink:to="us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentQuarterlyReport" xlink:to="dei_DocumentQuarterlyReport_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock" xlink:to="us-gaap_GoodwillAndIntangibleAssetsDisclosureTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ScheduleOfIncomeTaxExpenseBenefitAndEffectiveTaxRateTableTextBlock" xlink:to="altr_ScheduleOfIncomeTaxExpenseBenefitAndEffectiveTaxRateTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredIncomeTaxesAndTaxCredits" xlink:to="us-gaap_DeferredIncomeTaxesAndTaxCredits_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityFilerCategory" xlink:to="dei_EntityFilerCategory_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherCurrentLiabilitiesTableTextBlock" xlink:to="us-gaap_OtherCurrentLiabilitiesTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_CurrencyLossesOnAcquisitionRelatedIntercompanyLoans" xlink:to="altr_CurrencyLossesOnAcquisitionRelatedIntercompanyLoans_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BalanceSheetLocationDomain" xlink:to="us-gaap_BalanceSheetLocationDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_GainOnMarkToMarketAdjustmentOfContingentConsideration" xlink:to="altr_GainOnMarkToMarketAdjustmentOfContingentConsideration_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets" xlink:to="us-gaap_IncreaseDecreaseInOtherNoncurrentAssets_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SummaryOfOtherIntangibleAssetsTable" xlink:to="altr_SummaryOfOtherIntangibleAssetsTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SecuredCreditAgreementMember" xlink:to="altr_SecuredCreditAgreementMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_DebtInstrumentConvertibleConversionRatePrincipalAmount" xlink:to="altr_DebtInstrumentConvertibleConversionRatePrincipalAmount_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TradeNamesMember" xlink:to="us-gaap_TradeNamesMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NonoperatingIncomeExpense" xlink:to="us-gaap_NonoperatingIncomeExpense_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CapitalExpendituresIncurredButNotYetPaid" xlink:to="us-gaap_CapitalExpendituresIncurredButNotYetPaid_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_Liabilities_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:to="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_SpecialAdjustmentsInterestIncomeAndOther" xlink:to="altr_SpecialAdjustmentsInterestIncomeAndOther_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossTable" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_DebtInstrumentPrincipalOutstanding" xlink:to="altr_DebtInstrumentPrincipalOutstanding_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquity" xlink:to="us-gaap_StockholdersEquity_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife" xlink:to="us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProductConcentrationRiskMember" xlink:to="us-gaap_ProductConcentrationRiskMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:to="us-gaap_IntangibleAssetsNetExcludingGoodwill_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentsTextBlock" xlink:to="us-gaap_ScheduleOfErrorCorrectionsAndPriorPeriodAdjustmentsTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLoss" xlink:to="us-gaap_NetIncomeLoss_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpense" xlink:to="us-gaap_InterestExpense_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfConvertibleDebt" xlink:to="us-gaap_RepaymentsOfConvertibleDebt_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerAssetNetCurrent" xlink:to="us-gaap_ContractWithCustomerAssetNetCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementOfFinancialPositionAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:to="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EffectiveIncomeTaxRateContinuingOperations" xlink:to="us-gaap_EffectiveIncomeTaxRateContinuingOperations_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentRepurchasedFaceAmount" xlink:to="us-gaap_DebtInstrumentRepurchasedFaceAmount_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_InterestIncomeAndOther" xlink:to="altr_InterestIncomeAndOther_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NoncashOrPartNoncashAcquisitionsTable" xlink:to="us-gaap_NoncashOrPartNoncashAcquisitionsTable_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentRedemptionPricePercentage" xlink:to="us-gaap_DebtInstrumentRedemptionPricePercentage_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UseOfEstimates" xlink:to="us-gaap_UseOfEstimates_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxDisclosureTextBlock" xlink:to="us-gaap_IncomeTaxDisclosureTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestAndOtherIncome" xlink:to="us-gaap_InterestAndOtherIncome_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock" xlink:to="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesOneMember" xlink:to="altr_ConvertibleNotesHoldersConversionRightsUnderCircumstancesOneMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpenseDebtExcludingAmortization" xlink:to="us-gaap_InterestExpenseDebtExcludingAmortization_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisaggregationOfRevenueLineItems" xlink:to="us-gaap_DisaggregationOfRevenueLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseholdImprovementsMember" xlink:to="us-gaap_LeaseholdImprovementsMember_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_BusinessCombinationEstimatedPostCombinationExpense" xlink:to="altr_BusinessCombinationEstimatedPostCombinationExpense_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_CashPaidForRepurchaseAndRetirementOfCommonStock" xlink:to="altr_CashPaidForRepurchaseAndRetirementOfCommonStock_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueDisclosuresAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ReclassificationsOfTemporaryToPermanentEquity" xlink:to="us-gaap_ReclassificationsOfTemporaryToPermanentEquity_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:to="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RestatementDomain" xlink:to="srt_RestatementDomain_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:to="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BusinessAcquisitionAxis" xlink:to="us-gaap_BusinessAcquisitionAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_IncomeTaxDisclosureAbstract_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_lbl"/>
<link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="altr_EmployeeStockPurchasePlanLiabilities" xlink:to="altr_EmployeeStockPurchasePlanLiabilities_lbl"/>
</link:labelLink>
</link:linkbase>

1 Subsequent Filing that References this Filing

  As Of               Filer                 Filing    For·On·As Docs:Size             Issuer                      Filing Agent

 2/22/24  Altair Engineering Inc.           10-K       12/31/23  110:15M                                    Donnelley … Solutions/FA
↑Top
Filing Submission 0000950170-23-058280   –   Alternative Formats (Word / Rich Text, HTML, Plain Text, et al.)
Copyright © 2024 Fran Finnegan & Company LLC – All Rights Reserved.
About — Privacy — Redactions — Help — Fri., May 17, 9:34:50.2pm ET