SYSML21 — Various sementic constraints need to check isSubactionUsage

The constraint checkActionUsageSubactionSpecialization checks that the operation isSubactionUsage is true before requiring that an ActionUsage specialize Actions::Action::subactions. The operation isSubactionUsage not only checks the ActionUsage is composite and has an owningType that is an ActionDefinition or ActionUsage, but also ensures that the ActionUsage is not an entry or exit action. Various subclasses of ActionUsage have semantic constraints that require more specific specializations of subactions but do not include the condition that the usage is not an entry or exit action:

• checkCalculationUsageSubcalculationSpecialization
• checkRequirementUsageSubrequirementSpecialization
• checkCaseUsageSubcaseSpecialization
• checkAnalysisCaseUsageSubAnalysisCaseSpecialization
• checkVerificationCaseUsageSubVerificationCaseSpecialization
• checkUseCaseUsageSubUseCaseSpecialization