软件工程第四版第2章

Chapter2ModelingtheProcessandLifeCycleShariL.PfleegerJoanneM.Atlee4thEditionContents2.1TheMeaningofProcess2.2SoftwareProcessModels2.3ToolsandTechniquesforProcessModeling2.4PracticalProcessModeling2.5InformationSystemExample2.6RealTimeExample2.7WhatthisChapterMeansforYouChapter2ObjectivesWhatwemeanbya“process”Softwaredevelopmentproducts,processes,andresourcesSeveralmodelsofthesoftwaredevelopmentprocessToolsandtechniquesforprocessmodeling2.1TheMeaningofProcessAprocess:aseriesofstepsinvolvingactivities,constrains,andresourcesthatproduceanintendedouputofsomekindAprocessinvolvesasetoftoolsandtechniques2.1TheMeaningofProcess

ProcessCharacteristicsPrescribesallmajorprocessactivitiesUsesresources,subjecttosetofconstraints(suchasschedule)ProducesintermediateandfinalproductsMaybecomposedofsubprocesseswithhierarchyorlinksEachprocessactivityhasentryandexitcriteriaActivitiesareorganizedinsequence,sotimingisclearEachprocesshasguidingprinciples,includinggoalsofeachactivityConstraintsmayapplytoanactivity,resourceorproduct2.1TheMeaningofProcess

TheImportanceofProcessesImposeconsistencyandstructureonasetofactivitiesGuideustounderstand,control,examine,andimprovetheactivitiesEnableustocaptureourexperiencesandpassthemalong2.2SoftwareProcessModels

ReasonsforModelingaProcessToformacommonunderstandingTofindinconsistencies,redundancies,omissionsTofindandevaluateappropriateactivitiesforreachingprocessgoalsTotailorageneralprocessforaparticularsituationinwhichitwillbeused2.2SoftwareProcessModels

SoftwareLifeCycleWhenaprocessinvolvesbuildingasoftware,theprocessmaybereferredtoassoftwarelifecycleRequirementsanalysisanddefinitionSystem(architecture)designProgram(detailed/procedural)designWritingprograms(coding/implementation)Testing:unit,integration,systemSystemdelivery(deployment)Maintenance2.2SoftwareProcessModels

SoftwareDevelopmentProcessModelsWaterfallmodelVmodelPrototypingmodelOperationalspecificationTransformationalmodelPhaseddevelopment:incrementsanditerationsSpiralmodelAgilemethods2.2SoftwareProcessModels

WaterfallModelOneofthefirstprocessdevelopmentmodelsproposedWorksforwellunderstoodproblemswithminimalornochangesintherequirementsSimpleandeasytoexplaintocustomersItpresentsaveryhigh-levelviewofthedevelopmentprocesssequenceofprocessactivitiesEachmajorphaseismarkedbymilestonesanddeliverables(artifacts)2.2SoftwareProcessModels

WaterfallModel(continued)2.2SoftwareProcessModels

WaterfallModel(continued)ThereisnoiterationinwaterfallmodelMostsoftwaredevelopmentsapplyagreatmanyiterations2.2SoftwareProcessModels

Sidebar2.1DrawbacksofTheWaterfallModelProvidesnoguidancehowtohandlechangestoproductsandactivitiesduringdevelopment(assumesrequirementscanbefrozen)ViewssoftwaredevelopmentasmanufacturingprocessratherthanascreativeprocessThereisnoiterativeactivitiesthatleadtocreatingafinalproductLongwaitbeforeafinalproduct2.2SoftwareProcessModels

WaterfallModelwithPrototypeAprototypeisapartiallydevelopedproductPrototypinghelpsdevelopersassessalternativedesignstrategies(designprototype)usersunderstandwhatthesystemwillbelike(userinterfaceprototype)Protopypingisusefulforverificationandvalidation2.2SoftwareProcessModels

WaterfallModelwithPrototype(continued)Waterfallmodelwithprototyping2.2SoftwareProcessModels

VModelAvariationofthewaterfallmodelUsesunittestingtoverifyproceduraldesignUsesintegrationtestingtoverifyarchitectural(system)designUsesacceptancetestingtovalidatetherequirementsIfproblemsarefoundduringverificationandvalidation,theleftsideoftheVcanbere-executedbeforetestingontherightsideisre-enacted2.2SoftwareProcessModels

VModel(continued)2.2SoftwareProcessModels

PrototypingModelAllowsrepeatedinvestigationoftherequirementsordesignReducesriskanduncertaintyinthedevelopment2.2SoftwareProcessModels

OperationalSpecificiationModelRequirementsareexecuted(examined)andtheirimplicationevaluatedearlyinthedevelopmentprocessFunctionalityandthedesignareallowedtobemerged2.2SoftwareProcessModels

TransformationalModelFewermajordevelopmentstepsAppliesaseriesoftransformationstochangeaspecificationintoadeliverablesystemChangedatarepresentationSelectalgorithmsOptimizeCompileReliesonformalismRequiresformalspecification(toallowtransformations)2.2SoftwareProcessModels

TransformationalModel(continued)2.2SoftwareProcessModels

PhasedDevelopment:IncrementsandIterationsShortercycletimeSystemdeliveredinpiecesenablescustomerstohavesomefunctionalitywhiletherestisbeingdevelopedAllowstwosystemsfunctioninginparalleltheproductionsystem(releasen):currentlybeingusedthedevelopmentsystem(releasen+1):thenextversion2.2SoftwareProcessModels

PhasedDevelopment:IncrementsandIterations

(continued)2.2SoftwareProcessModels

PhasedDevelopment:IncrementsandIterations

(continued)Incrementaldevelopment:startswithsmallfunctionalsubsystemandaddsfunctionalitywitheachnewreleaseIterativedevelopment:startswithfullsystem,thenchangesfunctionalityofeachsubsystemwitheachnewrelease2.2SoftwareProcessModels

PhasedDevelopment:IncrementsandIterations

(continued)PhaseddevelopmentisdesirableforseveralreasonsTrainingcanbeginearly,eventhoughsomefunctionsaremissingMarketscanbecreatedearlyforfunctionalitythathasneverbeforebeenofferedFrequentreleasesallowdeveloperstofixunanticipatedproblemsglobalyandquicklyThedevelopmentteamcanfocusondifferentareasofexpertisewithdifferentreleases2.2SoftwareProcessModels

SpiralModelSuggestedbyBoehm(1988)CombinesdevelopmentactivitieswithriskmanagementtominimizeandcontrolrisksThemodelispresentedasaspiralinwhicheachiterationisrepresentedbyacircuitaroundfourmajoractivitiesPlanDeterminegoals,alternatives,andconstraintsEvaluatealternativesandrisksDevelopandtest2.2SoftwareProcessModels

SpiralModel(continued)2.2SoftwareProcessModels

AgileMethodsEmphasisonflexibilityinproducingsoftwarequicklyandcapablyAgilemanifesto(宣言)ValueindividualsandinteractionsoverprocessandtoolsPrefertoinvesttimeinproducingworkingsoftwareratherthaninproducingcomprehensivedocumentationFocusoncustomercollaborationratherthancontractnegotiationConcentrateonrespondingtochangeratherthanoncreatingaplanandthenfollowingit2.2SoftwareProcessModels

AgileMethods:ExamplesofAgileProcessExtremeprogramming(XP)Crystal:acollectionofapproachesbasedonthenotionthateveryprojectneedsauniquesetofpoliciesandconventionsScrum:30-dayiterations;multipleself-organizingteams;daily“scrum”coordinationAdaptivesoftwaredevelopment(ASD)2.2SoftwareProcessModels

AgileMethods:ExtremeProgrammingEmphasisonfourcharacteristicsofagilityCommunication:continualinterchangebetweencustomersanddevelopersSimplicity:selectthesimplestdesignorimplementationCourage:commitmenttodeliveringfunctionalityearlyandoftenFeedback:loopsbuiltintothevariousactivititesduringthedevelopmentprocess2.2SoftwareProcessModels

AgileMethods:TwelveFacetsofXPTheplanninggame(customerdefinesvalue)SmallreleasesMetaphor(commonvision,commonnames)SimpledesignWritingtestsfirstRefactoringPairprogrammingCollectiveownershipContinuousintegration(smallincrements)Sustainablepace(40hours/week)On-sitecustomerCodingstandards2.2SoftwareProcessModels

Sidebar2.2WhenisExtremeTooExtreme?Extremeprogramming'spracticesareinterdependentAvulnerabilityifoneofthemismodifiedRequirementsexpressedasasetoftestcasesmustbepassedbythesoftwareSystempassesthetestsbutisnotwhatthecustomerispayingforRefactoringissueDifficulttoreworkasystemwithoutdegradingitsarchitecture2.2SoftwareProcessModels

Sidebar2.3CollectionsofProcessModelsDevelopmentprocessisaproblem-solvingactivityCurtis,Krasner,andIscoe(1988)performedafieldstudytodeterminewhichproblem-solvingfactorstocapturedinprocessmodelTheresultssuggestalayeredbehavioralmodelassupplementtothetraditionalmodelProcessmodelshouldnotonlydescribeseriesoftasks,butalsoshoulddetailfactorsthatcontributetoaproject'sinherentuncertaintyandriskDiscussion:SelectingModels-1Foreachofthefollowing,whatlifecyclesmightcontributeusefulelements,andwhy?ProjectAisaddingthreeneweditfunctionsand5newprinteroptionstoanewreleaseofawordprocessingproduct.ProjectBisbuildingafoot-pedaloperatedmouse.Discussion:SelectingModels-2ProjectChastoincorporate3newdivisionsofthecompanythatwererecentlyacquiredintothecorporatenetworkstrategy.Eachofthedivisionshasitsownhomegrownhardwareandsoftware,andallaretobeconvertedtoacommontypeofserverandoperatingsystem.ProjectDneedstoupgradesoftwaretohelpindividualsfiletheirfederaltaxforms.Thenationallegislaturewillbemeetinguntilamonthbeforetheproducthastoship,decidingonlastminutechangestotaxrulesuntilthen.NotationdependsonwhatwewanttocaptureinthemodelThetwomajornotationcategoriesStaticmodel:depictstheprocessDynamicmodel:enactstheprocess2.3ToolsandTechniquesforProcessModelingElementsofaprocessareviewedintermsofseventypesActivitySequenceProcessmodelResourceControlPolicyOrganizationSeveraltemplates,suchasanArtifactDefinitionTemplate2.3ToolsandTechniquesforProcessModeling

StaticModeling:LaiNotation2.3ToolsandTechniquesforProcessModeling

StaticModeling:LaiNotation2.3ToolsandTechniquesforProcessModeling

StaticModeling:LaiNotation(continued)Theprocessofstartingacar2.3ToolsandTechniquesforProcessModeling

StaticModeling:LaiNotation(continued)TransitiondiagramillustratesthetransitionforacarEnablesenactionofprocesstoseewhathappenstoresourcesandartifactsasactivitiesoccurSimulatealternativesandmakechangestoimprovetheprocessExample:systemsdynamicsmodel2.3ToolsandTechniquesforProcessModeling

Dynamic

ModelingIntroducedbyForresterinthe1950'sAbdel-HamidandMadnickappliedittosoftwaredevelopmentOnewaytounderstandsystemdynamicsisbyexploringhowsoftwaredevelopmentprocessaffectsproductivity2.3ToolsandTechniquesforProcessModeling

Dynamic

Modeling:SystemDynamics2.3ToolsandTechniquesforProcessModeling

Dynamic

Modeling:SystemDynamics(continued)PictorialpresentationoffactorsaffectingproductivityArrowsindicatehowchangesinonefactorchangeanother2.3ToolsandTechniquesforProcessModeling

Dynamic

Modeling:SystemDynamics(continued)Asystemdynamicmodelcontainingfourmajorareasaffectingproductivity

2.3ToolsandTechniquesforProcessModeling

Sidebar2.4ProcessProgrammingAprogramtodescribeandenacttheprocessEliminateuncertaintyBasisofanautomatedenvironmenttoproducesoftwareDoesnotcaptureinherentvariabilityofunderlyingdevelopmentprocessImplementationenvironment,skill,experience,understandingthecustomerneedsProvidesonlysequenceoftasksGivesnowarningofimpendingproblems2.4PracticalProcessModeling

MarvelCaseStudiesUsesMarvelprocesslanguage(MPL)Threeconstructs:classes,rules,toolenvelopesThree-partprocessdescriptionrule-basedspecificationofprocessbehaviorobject-orienteddefinitionofmodel’sinformationprocesssetofenvelopestointerfacebetweenMarvelandexternalsoftwaretools2.4PracticalProcessModeling

MarvelCaseStudies(continued)InvolvedtwoAT&TnetworksnetworkcarriedphonecallssignalingnetworkresponsibleforroutingcallsandbalancingthenetworkloadMarvelwasusedtodescribethesignalingfaultresolution2.4PracticalProcessModeling

MarvelCaseStudies(continued)SignalingFaultResolutionProcess2.4PracticalProcessModeling

ExampleofMarvelCommands2.4PracticalProcessModeling

DesirablePropertiesofProcessModelingToolsandTechniquesFacilitateshumanunderstandingandcommunicationSupportsprocessimprovementSupportsprocessmanagementProvidesautomatedguidanceinperformingtheprocessSupportsautomatedprocessexecution2.5InformationSystemExample

PiccadillyTelevisionAdvertisingSystemNeedsasystemthatiseasilymaintainedandchangedRe