软件工程英文教程(6).ppt

ModellingDynamicsofObjects BuildingStateTransitionDiagrams DrLilySun2011 2012 LearningObjectives ToappreciatetheroleofmodellingdynamicsofanobjectinrelationtothesystemsdesignToestablishviewsonstablestatesofanobjectinitslifetimeduringwhichthestateschangedrivenbytheeventsTomodelsuchstateschangeinStateTransitionDiagramsToapplytheprinciplesandstyleguideofSateTransitionDiagramswhiledesignanddocumentthestatechangewhichinturnwillguidetheconstructionofcoding ModellingDynamicBehaviour ActivityDiagramshigh levelactivitiesaccomplishedbyhumanagentsand ormachineagentsinagivenbusinessdomainInteractionDiagrams e g SequenceDiagrams technicalfunctionsperformedbysoftwaresystemsthesetechnicalfunctionsarerealisedbytheinteraction messagepassing betweentheinvolvingobjectsinlogicalsequencesStateTransitionDiagramsAneffecttoanobjectcausedbyactionstriggeredbyeventstosatisfycertainconditions ModellingtheBehaviourofanObject Softwaresystemsareevent drivencontinuouslywaitfortheoccurrenceofsomeexternalorinternalevent suchasamouseclickabuttonpressatimetickanarrivalofadatapacketposttoamanipulationonobjects aresultantvalue i e effect reflectsastatusoftheobjectatthepresentmomentStatesofanobjectanobjectmayholdanumberofstateswhichrepresentsthecorrespondingsituationoftheobjectastatecanbecausedbyoneeventorthedifferenteventsundercertainconditions StateTransitionDiagrams Behaviouralstatemachinetospecifytheseriousstatesthatanobjectgoesthroughduringitslifetimeinresponsetoeventsdifferenteventstriggertheobjecttoholdcorrespondingstates i e resultsofmanipulations TomodelstatesofanobjectanditsreactionstomessagesorothereventsduringitslifetimeToestablishboundariesoftheexistenceofanobject startandfinishstate Toanalyseevents actions andguardconditionsassociatedwiththetransitionbetweenthestatesoftheobject ConceptsforStateTransitionDiagrams Stateaconditionorasituationduringthelifeofanobjectduringitslife theobjectsatisfiessomecondition performssomeactionorwaitsforsomeevent message InitialStaterepresentthepointatwhichanobjectbeginstoexistFinalStaterepresentthepointfromwhichanobjectbeginstoceasealltheactions aState ConceptsforStateTransitionDiagrams cont Eventisanoccurrencethatisrelevanttotheobjectandtriggersactionsintheobjectexternalevent knownasasystemevent causedbysomething e g actor outsidethesystemboundaryinternalevent causedbysomethinginsidethesystemboundarywhenanoperationisinvokedviamessagethatwassentfromanotherinternalobjecttemporalevent causedbytheoccurrenceofaspecificdateandtimeorpassageoftime anEvent ConceptsforStateTransitionDiagrams cont Actionisanexecutableatomiccomputationoperationcallstheconstructionordestructionofanotherobject orthesendingofasignaltoanobjectTypesofActionentryeffectexecuteduponentrytoastate nomatterwhichtransitionledyouinexiteffectexecuteduponexitfromastate nomatterwhichtransitionledyouawaydo activityeffectisanongoingactivitycarriedoutbytheobjectthisactivitywillcontinuetillitisinterruptedbyanevent anAction ConceptsforStateTransitionDiagrams cont Transitionisarelationshipbetweentwostatesindicatingthatanobjectinthefirststatewillperformcertainactionsandenterthesecondstatewhenaspecialeventoccursandspecificconditionsaresatisfiedsourcestateinitiateantransitionwhichtriggeraneventtargetstatethestatethatisactiveafterthecompletionofthetransitioneventtriggertheeventwhoserecognitionbytheobjectinthesourcestatemakesthetransitioneligibletofire providingitsguardconditionissatisfiedguardconditionaBooleanexpression true thetransitioniseligibletofire false donotfire anEvent ConceptsforStateTransitionDiagrams cont Framethecontext scope withinwhichthestatebehaviourismodelledIsnormallyfocusedonONEobject context GuidelinesforCreationofStateTransitionDiagrams Setacontext i e selectoneobject Identifytheinitial final andstablestatesoftheobjectwithinthecontextDeterminetheorderinwhichtheobjectwillpassthroughthestablestatesIdentifytheevents actions andguardconditionsassociatedwiththetransitionsValidatethestatebehaviourreferringtotheclassmodelandtheusecasemodel IllustrationofaStateTransitionDiagram Order ConcurrentStatesintheirTransitions ArticulatingConcerningObjects Order OrderItem Item Customer 11 0 1 0 1 places describes order id stringorderDate datecustomer id stringorderStatus string updateStatus e event oI id stringitem id stringquantity intprice currency item id stringitemName stringdescription stringunitPrice currency AnalysisofEventsandStatesforObjects Order persistent orderStatus string updateStatus e event Monitoringthisstatechange executingtheactionstochangethepreviousstateintoaresultantstate Stage1SelectaclassIdentifyaninterestofstatechange Order persistent add remove update find updateStatus e event order id stringorderDate datecustomer id stringorderStatus string AnalysisofEventsandStatesforObjects cont Stage2Identifythepossibleevents Order persistent orderStatus string updateStatus e event trigger event changethepreviousstate processthecurrentevent AnalysisofEventsandStatesforObjects cont Stage3Identifythestablestatesastheresultsoftheeventoccurrences Order persistent orderStatus string updateStatus e event trigger byevent changethepreviousstate processthecurrentevent Alistofstablestates receivedapprovedpendingconsolidateddeliveredinvoicedpaidcancelled TheStateTransitionDiagram Example1 theflatstatemachine paid received invoiced consolidated approved theorderbeencreatedbythecustomer srequest theorderbeensentforapproval proceedtheorder thecustomerbeenrequestedforfurtherinformation Order pending thecustomerprovedfurtherinformation cancelled thecustomerwithdrawn theorderterminated delivered theinvoicebeencreated theorderbeenconsolidated theorderbeendispatched thecustomerpaid thepaymentconfirmed thecustomerreceivedtheorder theorderclosed PseudoCodesforStateTransitions typedeforder s start s received s approved s pending s consolidated s delivered s invoiced s cancelled s paid AND delivered s closed STATES updateStatus e event casee ordercreated orderStatus received endcase casee sentforapproval ifitisapprovedthenorderStatus approved ifthecustomerisrequiredtoprovidefurtherinformationthenorderStatus pending endcase PseudoCodesforStateTransitions casee proceedorder docreateInvoice messagetoPaymentobject docreateConsolidation messagetoShippingobject if theinvoiceiscreate AND theorderisconsolidated thenorderStatus invoiced AND consolidated endcase casee customerwithdrawn orderStatus cancelled iftheorderhasnotbeenproceededthentheorderterminatedelsesendmessagestotherelevantobjectsformodificationsendcase PseudoCodesforStateTransitions cont casee thecustomerpaid orderStat