8/4/2015 HowtoDrawUMLUseCaseDiagramDetermineSubjectBoundaries,DefineActors,DescribeUseCases.

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HowtoDrawUMLUseCaseDiagramThereareseveralapproachesonhowtodrawUMLusecasediagrams.Ifyoudon'tknowfromwheretostart,trytofollowthestepsdescribedhere.

DefineSubjectSubjectisabusiness,softwaresystem,subsystem,component,device,etc.thatwearedesigningorjusttryingtounderstandhowitisworking.Itisveryimportanttodefinewhatkindofsystemitis,andwhatisitsscopeorboundary.Giveitapropername,anduseappropriatestereotype,e.g.BusinessorSubsystem.

Forexample,wewanttodescribeaPharmacy,anditisnotsoftwarepharmacyprescriptionsystembutactualpharmacybusiness.So,wewilldrawitasshownbelow,usingBusinessstereotype.

BusinessPharmacyasUMLsubject.

AnotherexampleofasubjectshownbelowisTicketvendingmachine,i.e.vendingmachinethatsellsandproducesticketstocommuters.Thiskindofmachineisacombinationofbothhardwareandsoftware,anditisonlyapartofthewholesystemsellingticketstothecustomers.SowewilluseSubsystemstereotype.

TicketvendingmachineasUMLsubject.

HerearesomeotherexamplesofUMLsubjectname:DepartmentStoreAirportAutomatedTellerMachine(ATM)PointofSale(POS)TerminalOnlineTravelReservationSystemElectronicPrescriptionService

Bydeclaringasubjectwearedefiningboundariesofthesystem,tobeabletodeterminewhatorwhoisinsidethesystem,andwhatorwhoisoutsideofit.

DefineActorsUMLactorissometype,grouporparticularfacetofusersthatrequiresomeservicesfromthesubject.Actorisanexternalentity,whichcouldbeahumanuserofthedesignedsystem,orsomeothersystemordeviceusingoursystem.

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ForthePharmacybusinesswedefinedabove,Customerisanexampleofanactor.Customerusesservicesprovidedbypharmacy.Pharmacistworkinginthepharmacyisnotanactor,heorsheispartofthebusinessandisusuallycalledbusinessworker.

CustomerisabusinessactorforthePharmacybusiness.

Ticketvendingmachineallowscommuterstobuytickets.SoCommuterisouractorinthiscase.

Commuterisanactorfortheticketvendingmachine.

Actorsshouldhavenamesaccordingtotheroletheyplayinrelationtooursystem.Examplesofactornames(userroles):SupplierPassengerReceptionistWebClientBankPaymentAuthorizationSystem

DefineUseCasesNowaswedefinedtheboundariesofthesystemthatwearedesigningoranalysing,andexternalusersofthesystem,weneedtodefinewhatdothoseusersneedfromthesystem.Eachusecasespecifiesaunitofcompleteandusefulfunctionalitythatthesubjectprovidestotheactor(s).Usecaseshouldreflectuserneedsandgoals,andshouldbeinitiatedbyanactor.

Forthepharmacycustomerabusinessusecasewouldbetogetsomemedicine.SoweareaddingProcureMedicinesbusinessusecase.BusinessactorCustomerparticipatinginthebusinessusecaseshouldbeconnectedtotheusecasebyassociation.

BusinessusecaseProcureMedicinesfortheCustomerofthePharmacybusiness.

TheultimategoaloftheCommuterinrelationtoourticketvendingmachineistobuyaticket.SoweareaddingPurchaseTicketusecase.Purchasingticketmightinvolveabank,ifpaymentistobemadeusingadebitorcreditcard.SowearealsoaddinganotheractorBank.Bothactorsparticipatingintheusecaseshouldbeconnectedtotheusecasebyassociation.

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TicketvendingmachineprovidesPurchaseTicketusecasefortheCommuterandBankactors.

Toplevelusecasesshoulddescribecompleteunitoffunctionalityprovidedtotheactor.Examplesofusecasenames:HireEmployeeTransferFundsFindBookMakeTravelReservationsSchedulePatientAppointment

DescribeUseCaseBehaviorsUsecasebehaviorsmaybedescribedinanaturallanguagetext(opaquebehavior),whichiscurrentcommonpractice,orbyusingUMLbehaviordiagramsforspecificbehaviorssuchasactivity,statemachine,interaction.

UMLtoolsshouldallowlinkingbehaviorstothedescribedusecase.ExampleofsuchbindingofausecasetothebehaviorrepresentedbyactivityisshownbelowusingUML2.5notation.

PurchaseTicketusecaseownsbehaviorrepresentedbyPurchaseTicketactivity.

PurchaseTicketactivitydiagramexamplebelowdescribesbehaviorofthePurchaseTicketusecase.

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ExampleofPurchaseTicketusecasebehaviordescribedusingactivitydiagram.

Usecasediagramsexamples

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byKirillFakhroutdinovThisdocumentdescribesUML2.5andisbasedonOMGUnifiedModelingLanguage(OMGUML)2.5specification [UML2.5FTFBeta1].AllUMLdiagramswerecreatedinMicrosoftVisio2007or2010using UML2.2stencils.Youcansendyourcommentsandsuggestionstowebmasteratwebmaster@umldiagrams.org.

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