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  <xs:element id="appn_DocumentAndEntityInformationTable" abstract="true" name="DocumentAndEntityInformationTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="appn_IncreaseDecreaseInAccruedCompensationAndRelatedBenefits" abstract="false" name="IncreaseDecreaseInAccruedCompensationAndRelatedBenefits" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_CapitalizedContractCostDeferrals" abstract="false" name="CapitalizedContractCostDeferrals" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_AggregateIntrinsicValueAbstract" abstract="true" name="AggregateIntrinsicValueAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="appn_DefinedContributionPlanEmployersMatchingContributionAnnualVestingTerm" abstract="false" name="DefinedContributionPlanEmployersMatchingContributionAnnualVestingTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="appn_IncreaseDecreaseInDeferredCommissions" abstract="false" name="IncreaseDecreaseInDeferredCommissions" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_RobertKramerMember" abstract="true" name="RobertKramerMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="appn_AuditInformationAbstract" abstract="true" name="AuditInformationAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="appn_SecuredTermLoanFacilityMember" abstract="true" name="SecuredTermLoanFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="appn_NumberOfVotesEntitledToStockholders" abstract="false" name="NumberOfVotesEntitledToStockholders" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="appn_ShareBasedPaymentArrangementTrancheFourMember" abstract="true" name="ShareBasedPaymentArrangementTrancheFourMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="appn_JudgmentPreservationInsuranceThresholdAmount" abstract="false" name="JudgmentPreservationInsuranceThresholdAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_CapitalizedContractCostRollForward" abstract="true" name="CapitalizedContractCostRollForward" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="appn_SummaryOfSignificantAccountingPoliciesLineItems" abstract="true" name="SummaryOfSignificantAccountingPoliciesLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="appn_YouyongZouLitigationMember" abstract="true" name="YouyongZouLitigationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="appn_TwoThousandSevenStockOptionPlanMember" abstract="true" name="TwoThousandSevenStockOptionPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="appn_PegasystemsLitigationMember" abstract="true" name="PegasystemsLitigationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="appn_GovernmentAgenciesMember" abstract="true" name="GovernmentAgenciesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="appn_AccruedCapitalExpendituresCurrent" abstract="false" name="AccruedCapitalExpendituresCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_MaintenanceAndSupportMember" abstract="true" name="MaintenanceAndSupportMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="appn_TenantImprovementsReimbursementsReceived" abstract="false" name="TenantImprovementsReimbursementsReceived" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_LitigationJudgmentPreservationInsuranceCost" abstract="false" name="LitigationJudgmentPreservationInsuranceCost" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_CustomerOneMember" abstract="true" name="CustomerOneMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="appn_IncreaseDecreaseInOperatingLeaseAssetsAndLiabilities" abstract="false" name="IncreaseDecreaseInOperatingLeaseAssetsAndLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_OperatingLossCarryforwardsExpirations" abstract="false" name="OperatingLossCarryforwardsExpirations" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_AccruedLegalCostsCurrent" abstract="false" name="AccruedLegalCostsCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantedInPeriodFairValue" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantedInPeriodFairValue" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_OperatingLeaseInterestExpense" abstract="false" name="OperatingLeaseInterestExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="appn_DebtInstrumentFaceAmountIncrease" abstract="false" name="DebtInstrumentFaceAmountIncrease" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
