UML建模技术第2章

.,Chapter2.IntroducingtheUML,OverviewoftheUMLThreestepstounderstandingtheUMLSoftwarearchitectureThesoftwaredevelopmentprocess,.,Introduction,TheUnifiedModelingLanguage(UML)isastandardlanguageforwritingsoftwareblueprints.TheUMLisappropriateformodelingsystemsrangingfromenterpriseinformationsystemstodistributedWeb-basedapplicationsandeventohardrealtimeembeddedsystems.,.,Eventhoughitisexpressive,theUMLisnotdifficulttounderstandandtouse.LearningtoapplytheUMLeffectivelystartswithformingaconceptualmodelofthelanguage,whichrequireslearningthreemajorelements:theUMLsbasicbuildingblocks,therules,somecommonmechanisms.,.,TheUMLisprocessindependent,althoughoptimallyitshouldbeusedinaprocessthatisusecasedriven,architecture-centric,iterative,andincremental.,.,2.1AnOverviewoftheUML,TheUMLisalanguageforVisualizingSpecifyingConstructingDocumentingtheartifactsofasoftware-intensivesystem.,.,2.1.1TheUMLIsaLanguage,Alanguageprovidesavocabularyandtherulesforcombiningwordsinthatvocabularyforthepurposeofcommunication.Amodelinglanguageisalanguagewhosevocabularyandrulesfocusontheconceptualandphysicalrepresentationofasystem.AmodelinglanguagesuchastheUMListhusastandardlanguageforsoftwareblueprints.,.,Modelingyieldsanunderstandingofasystem.Noonemodeliseversufficient.ThevocabularyandrulesofalanguagesuchastheUMLtellyouhowtocreateandreadwell-formedmodels,buttheydonttellyouwhatmodelsyoushouldcreateandwhenyoushouldcreatethem.Thatstheroleofthesoftwaredevelopmentprocess.,.,2.1.2TheUMLIsaLanguageforVisualizing,Formanyprogrammers,thedistancebetweenthinkingofanimplementationandthenpoundingitoutincodeisclosetozero.However,thereareseveralproblemswiththis:First,communicatingthoseconceptualmodelstoothersiserror-proneunlesseveryoneinvolvedspeaksthesamelanguage.Second,therearesomethingsaboutasoftwaresystemyoucantunderstandunlessyoubuildmodelsthattranscendthetextualprogramminglanguage.Third,ifthedeveloperwhocutthecodeneverwrotedownthemodelsthatareinhisorherhead,thatinformationwouldbelostforeveror,atbest,onlypartiallyrecreatablefromtheimplementationoncethatdevelopermovedon.,.,WritingmodelsintheUMLaddressesthethirdissue:Anexplicitmodelfacilitatescommunication.Somethingsarebestmodeledtextually;othersarebestmodeledgraphically.TheUMLissuchagraphicallanguage.TheUMLismorethanjustabunchofgraphicalsymbols.Rather,behindeachsymbolintheUMLnotationisawell-definedsemantics.,.,2.1.3TheUMLIsaLanguageforSpecifying,Inthiscontext,specifyingmeansbuildingmodelsthatareprecise,unambiguous,andcomplete.Inparticular,theUMLaddressesthespecificationofalltheimportantanalysis,design,andimplementationdecisionsthatmustbemadeindevelopinganddeployingasoftware-intensivesystem.,.,2.1.4TheUMLIsaLanguageforConstructing,TheUMLisnotavisualprogramminglanguage,butitsmodelscanbedirectlyconnectedtoavarietyofprogramminglanguages.ThismappingpermitsforwardengineeringthegenerationofcodefromaUMLmodelintoaprogramminglanguage.Thereverseisalsopossible:YoucanreconstructamodelfromanimplementationbackintotheUML.,.,2.1.5TheUMLIsaLanguageforDocumenting,Ahealthysoftwareorganizationproducesallsortsofartifactsinadditiontorawexecutablecode.Theseartifactsinclude(butarenotlimitedto)RequirementsArchitectureDesignSourcecodeProjectplansTestsPrototypesReleasesTheUMLaddressesthedocumentationofasystemsarchitectureandallofitsdetails.,.,2.1.6WhereCantheUMLBeUsed?,TheUMLisintendedprimarilyforsoftware-intensivesystems.IthasbeenusedeffectivelyforsuchdomainsasEnterpriseinformationsystemsBankingandfinancialservicesTelecommunicationsTransportationDefense/aerospaceRetailMedicalelectronicsScientificDistributedWeb-basedservicesTheUMLisnotlimitedtomodelingsoftware.,.,2.2AConceptualModeloftheUML,TounderstandtheUML,youneedtoformaconceptualmodelofthelanguage,andthisrequireslearningthreemajorelements:theUMLsbasicbuildingblocks,therulesthatdictatehowthosebuildingblocksmaybeputtogether,andsomecommonmechanismsthatapplythroughouttheUML.,.,2.2.1BuildingBlocksoftheUML,ThevocabularyoftheUMLencompassesthreekindsofbuildingblocks:ThingsRelationshipsDiagramsThingsaretheabstractionsthatarefirst-classcitizensinamodel;relationshipstiethesethingstogether;diagramsgroupinterestingcollectionsofthings.,.,1)ThingsintheUML,Structuralthings:thenounsofUMLmodelsBehavioralthings:thedynamicpartsofUMLmodelsGroupingthings:theorganizationalpartsofUMLmodelsAnnotationalthings:theexplanatorypartsofUMLmodels,.,2)RelationshipsintheUML,DependencyAssociationGeneralizationRealization,.,3)DiagramsintheUML,Adiagramisthegraphicalpresentationofasetofelements,mostoftenrenderedasaconnectedgraphofvertices(things)andpaths(relationships).Youdrawdiagramstovisualizeasystemfromdifferentperspectives,soadiagramisaprojectionintoasystem.,.,ClassdiagramObjectdiagramComponentdiagramCompositestructurediagramUsecasediagramSequencediagramCommunicationdiagramStatediagramActivitydiagramDeploymentdiagramPackagediagramTimingdiagramInteractionoverviewdiagram,.,2.2.2RulesoftheUML,TheUMLsbuildingblockscantsimplybethrowntogetherinarandomfashion.Likeanylanguage,theUMLhasanumberofrulesthatspecifywhatawell-formedmodelshouldlooklike.Awell-formedmodelisonethatissemanticallyself-consistentandinharmonywithallitsrelatedmodels.,.,TheUMLhassyntacticandsemanticrulesforNames-Whatyoucancallthings,relationships,anddiagramsScope-ThecontextthatgivesspecificmeaningtoanameVisibility-HowthosenamescanbeseenandusedbyothersIntegrity-HowthingsproperlyandconsistentlyrelatetooneanotherExecution-WhatitmeanstorunorsimulateadynamicmodelTherulesoftheUMLencourageyoubutdonotforceyoutoaddressthemostimportantanalysis,design,andimplementationquestionsthatpushsuchmodelstobecomewell-formedovertime.,.,2.2.3CommonMechanismsintheUML,SpecificationsAdornmentsCerfaceandimplementation.typeandrole.ExtensibilitymechanismsStereotypesTaggedvaluesConstraints,.,Naturally,itsimportantthatyoudosoincontrolledwayssothatthroughtheseextensions,youremaintruetotheUMLspurposethecommunicationofinformation.,.,2.3Architecture,Visualizing,specifying,constructing,anddocumentingasoftware-intensivesystemdemandsthatthesystembeviewedfromanumberofperspectives.Asystemsarchitectureisperhapsthemostimportantartifactthatcanbeusedtomanagethesedifferentviewpointsandthuscontroltheiterativeandincrementaldevelopmentofasystemthroughoutitslifecycle,.,ArchitectureisthesetofsignificantdecisionsaboutTheorganizationofasoftwaresystemTheselectionofthestructuralelementsandtheirinterfacesbywhichthesystemiscomposedTheirbehavior,asspecifiedinthecollaborationsamongthoseelementsThecompositionofthesestructuralandbehavioralelementsintoprogressivelylargersubsystemsThearchitecturalstylethatguidesthisorganization:thestaticanddynamicelementsandtheirinterfaces,theircollaborations,andtheircomposition,.,Figure2-23.ModelingaSystemsArchitecture,.,2.4SoftwareDevelopmentLifeCycle,TheUMLislargelyprocess-independent,meaningthatitisnottiedtoanyparticularsoftwaredevelopmentlifecycle