最新ch05ExtendingtheRequirementsModels教学讲义PPT课件.ppt

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1、ch05ExtendingtheRequirementsModels1UseCaseDescriptionsAlistofusecasesandusecasediagramsprovidesanoverviewofalltheusecasesforasystem.Ausecasedescriptionlistsanddescribestheprocessingdetailsforausecase.UseCaseDescriptionAtextualmodelthatlistsanddescribestheprocessingdetailsforausecase1UseCaseDesc

2、riptionsAnactorisalwaysoutsidetheautomationboundaryofthesystembutmaybepartofthemanualportionofthesystem.Bydefiningactorsthatway—asthosewhointeractwiththesystem—wecanmorepreciselydefinetheexactinteractionstowhichtheautomatedsystemmustrespond.Thistighterfocushelpsdefinethespecificrequirementsofth

3、eautomatedsystemitself—torefinethemaswemovefromtheeventtabletotheusecasedetails.2021/8/122021/8/12PreconditionsandPostconditionPreconditionsandPostconditionsprovidecriticalinformationaboutthestateofthesystembeforeandaftertheusecaseexecutes.Preconditionsidentifywhatthestateofthesystemmustbeforth

4、eusecasetobegin,includingwhatobjectsmustalreadyexist,whatinformationmustbeavailable,andeventheconditionoftheactorpriortobeginningtheusecase.Postconditionsidentifywhatmustbetrueuponcompletionoftheusecase.2021/8/12PreconditionsandPostconditionMostimportantly,postconditionsindicatewhatnewobjectsar

5、ecreatedorupdatedbytheusecaseandhowobjectsneedtobeassociated.Thepostconditionsareimportantfortworeasons.Thebasisforstatingtheexpectedresultsfortestcasesthatwillbeusedfortestingtheusecaseafteritisimplemented.Theobjectsinpostconditionsindicatewhichobjectsinvolvedintheusecaseareimportantfordesign.

6、2021/8/122021/8/122021/8/122ActivityDiagramsforUseCasesActivitydiagramsareastandardUMLdiagram,andtheyarealsoaneffectivetechniquetodocumenttheflowofactivitiesforeachusecase.Sometimes,anactivitydiagramcantaketheplaceoftheflowofactivitiessectionofausecasedescription,andsometimes,itiscreatedtosuppl

7、ementtheusecasedescription.ActivitydiagramforCreatecustomeraccountshowingalternatewaytomodeltheflowofactivities2021/8/12ActivitydiagramforFillshoppingcartshowingricheruserexperienceTheyellowovalsshowtheotherusecasesthatareinvokedw