面向对象系统分析与设计

面向对象系统分析与设计,河北农业大学信息科学与技术学院,主要内容,1、系统分析与设计概论2、面向对象概念与术语3、面向对象分析与设计4、面向对象编程5、UML面向对象设计基础6、UML面向对象开发,系统分析与设计概论(SystemAnalysisandDesign),ChapterObjectives(Youshouldbeableto)1.Defineasystem,informationsystem,andautomatedinformationsystem.2.Definethebasiccomponentsandthebasiccharacteristicsofanautomatedinformationsystem.3.Definesystemanalysisanddesignanddiscusswhyitisadifficulthumanendeavor.4.Describetheskillsandactivitiesofasystemanalyst.,系统分析与设计概论(SystemAnalysisandDesign),5.Describeageneralmodeloftheanalysis,design,andimplementationprocess.6.Discusssystemsanalysisanddesignasacareer.7.Discusswhatasystemanalystdoes.8.Discusssystemsanalysisanddesignprojectsandwheretheycomefrom.9.Discusstheneedforcreatinginformationsystemsrequirementsspecifications.,系统分析与设计概论(SystemAnalysisandDesign),10.Defineanddescribetheinformationsystemslifecycle.11.Defineanddescribetheinformationsystemdevelopmentlifecycle.12.Discusstheprinciplesusedtoguidesystemanalysisanddesign.,系统分析与设计概论(SystemAnalysisandDesign),DevelopmentProcessSystemsplanningSystemsanalysisSystemdesignSystemsimplementationSystemsevolution,系统分析与设计概论(SystemAnalysisandDesign),2.ConceptofSystemAnalysisandDesignWhatisasystem?Asystemisasetofinterrelatedcomponents,workingtogetherforacommonpurpose.Therearetwotypesofsystems:naturalandfabricated.,系统分析与设计概论(SystemAnalysisandDesign),SystemModelwithSixComponents:,system,boundary,controls,processing,inputs,feedback,outputs,系统分析与设计概论(SystemAnalysisandDesign),Whatisaninformationsystem?Aninformationsystemisatypeoffabricatedsystemthatisusedbyoneormorepersonstohelpaccomplishataskorassignment.,系统分析与设计概论(SystemAnalysisandDesign),Whatisaninformationsystem?,data,people,procedures,系统分析与设计概论(SystemAnalysisandDesign),Whatisanautomatedinformationsystem?Aautomatedinformationsystemisaninformationsystemthatincorporatestheuseofcomputerhardwareandsoftwareaspartofthesystem.,系统分析与设计概论(SystemAnalysisandDesign),Whatisanautomatedinformationsystem?,data,people,software,procedures,hardware,系统分析与设计概论(SystemAnalysisandDesign),Whatarethebasiccharacteristicsofaninformationsystem?Thebasiccharacteristicsthatexistwithinaninformationsystemaredata,functions,andbehavior,asillustratedinthefollowingfigure.,Data,Functions,Behavior,系统分析与设计概论(SystemAnalysisandDesign),Whatarethebasiccharacteristicsofaninformationsystem?Data:input,stored,oroutputFunction:businessactivityperformedBehavior:theobservableeffectsofarequest,系统分析与设计概论(SystemAnalysisandDesign),Whatissystemsanalysisanddesign?Systemanalysisanddesignisaboutdevelopingsoftware,butitismoreaboutdevelopingacompleteautomatedinformationsystem,whichincludeshardware,software,people,procedures,anddata.Thesefivecomponentsexistinvirtuallyallautomatedinformationsystems,althoughtheamountofeachwillvarywithrespecttothespecificsystembeingdeveloped.Allofthesecomponentsmustbeconsideredandaddressedduringsystemanalysisanddesign.,系统分析与设计概论(SystemAnalysisandDesign),Actorsofsystemsanalysisanddesign?SystemAnalyst;SystemEngineer;Programmer;Architect;,系统分析与设计过程,系统分析与设计过程,系统分析与设计概论(SystemAnalysisandDesign),Whatmakessystemsanalysisanddesignsuchadifficulthumanendeavor?Sevenreasons:1.Analysisproblems,attheirinception,haveill-definedboundariesandstructure(usersarenotcertainofwhattheywant),andhaveasufficientdegreeofuncertaintyaboutthenatureofthesolution.,系统分析与设计概论(SystemAnalysisandDesign),Whatmakessystemsanalysisanddesignsuchadifficulthumanendeavor?2.Thesolutionssystemsanalystscomeupwithtosolvetheproblemsareartificial,andsincetheyaredesignedbyhumanswithdifferentbackgrounds,experiences,biases,andsoon,thereexistsanendlessvarietyofpotentialsolutions.Thatmeansthatthereisnosinglecorrectsolutiontoaproblem.ManyneedsandManysolutions.,系统分析与设计概论(SystemAnalysisandDesign),Whatmakessystemsanalysisanddesignsuchadifficulthumanendeavor?3.Analysisproblemsaredynamic.Nobusinessisstandingstill.Change!4.Thesolutionstoanalysisproblemsrequireinterdisciplinaryknowledgeandskills,hence,theneedforateamapproachtoISdevelopment.EmphasisonthepartnershipconceptbetweentheusercommunityandtheISdevelopers.,系统分析与设计概论(SystemAnalysisandDesign),Whatmakessystemsanalysisanddesignsuchadifficulthumanendeavor?5.Theknowledgebaseofthesystemsanalysisiscontinuallyevolving.Astheapprenticesystemsanalystprogressesthroughthejunior,associate,andseniorsystemsanalystranksovertime,heorshecontinuestolearnmoreaboutbusinessproblemdomainsaswellasimprovinghisorheranalyticalskillsandsoftwaredevelopmenttoolandtechniqueskills.,系统分析与设计概论(SystemAnalysisandDesign),Whatmakessystemsanalysisanddesignsuchadifficulthumanendeavor?6.Theprocessofanalysisisprimarilyacognitiveactivityinthatweareaskedto(1)putstructuretoanabstractproblemdomain,(2)processdiverseinformationfromavarietyofusers,and(3)developalogicalandconsistentspecificationthatwillleadtothecreationofasuccessfulinformationsystem.7.ThePeople!Studyhumanandorg.behavior.,Stakeholders:PlayersintheSystemsDevelopmentTeam,Astakeholderisanypersonwhohasaninterestinanexistingornewinformationsystem.Stakeholderscanbetechnicalornontechnicalworkers.Forinformationsystems,thestakeholderscanbeclassifiedas(sixgroupsofinformationworkers):SystemownersSystemusersSystemsanalystsSystemdesignersSystembuildersITvendorsandconsultants,InformationversusKnowledgeWorkers,Informationworkersarethoseworkerswhosejobsinvolvethecreation,collection,processing,distribution,anduseofinformation.(InUSAtheyaresocalled),Knowledgeworkersareasubsetofinformationworkerswhoseresponsibilitiesarebasedonaspecializedbodyofknowledge.(Collegeeducated;Dependingoninformationandabilitytoproperlyuseandreacttoinformation),SystemOwners,Systemownersaretheinformationsystemssponsorsandchiefadvocates.Theyareusuallyresponsibleforfundingtheprojecttodevelop,operate,andmaintaintheinformationsystem.,SystemUsers,Systemusersarethepeoplewhouseorareaffectedbytheinformationsystemonaregularbasiscapturing,validating,entering,respondingto,storing,andexchangingdataandinformation.Acommonsynonymisclient.Typesinclude:InternalusersClericalandserviceworkersTechnicalandprofessionalstaffSupervisors,middlemanagers,andexecutivemanagersRemoteandmobileusers(internalbutdisconnected)Externalusers(customerandothersystemusers),SystemDesignersandSystemBuilders,Systemdesignerstranslatesystemusersbusinessrequirementsandconstraintsintotechnicalsolutions.Theydesignthecomputerfiles,databases,inputs,outputs,screens,networks,andprogramsthatwillmeetthesystemusersrequirements.Systembuildersconstructtheinformationsystemcomponentsbasedonthedesignspecificationsfromthesystemdesigners.Inmanycases,thesystemdesignerandbuilderforacomponentareoneandthesame.,SystemsAnalysts,Asystemsanalyststudiestheproblemsandneedsofanorganizationtodeterminehowpeople,data,processes,communications,andinformationtechnologycanbestaccomplishimprovementsforthebusiness.Wheninformationtechnologyisused,theanalystisresponsiblefor:Theefficientcaptureofdatafromitsbusinesssource,Theflowofthatdatatothecomputer,Theprocessingandstorageofthatdatabythecomputer,andTheflowofusefulandtimelyinformationbacktothebusinessanditspeople.,VariationsontheSystemsAnalystsTitle,Abusinessanalystisasystemsanalystthatspecializesinbusinessproblemanalysisandtechnology-independentrequirementsanalysis.Aprogrammer/analyst(oranalyst/programmer)includestheresponsibilitiesofboththecomputerprogrammerandthesystemsanalyst.Othersynonymsforsystemsanalystinclude:SystemsconsultantSystemsarchitectSystemsengineerInformationengineerSystemsintegrator,Problem-SolvingScenarios,Trueproblemsituations,eitherrealoranticipated,thatrequirecorrectiveactionOpportunitiestoimproveasituationdespitetheabsenceofcomplaintsDirectivestochangeasituationregardlessofwhetheranyonehascomplainedaboutthecurrentsituation,GeneralProblem-SolvingApproach,1.Identifytheproblem.2.Analyzeandunderstandtheproblem.3.Identifysolutionrequirementsorexpectations.4.Identifyalternativesolutionsanddecideacourseofaction.5.Designandimplementthe“best”solution.6.Evaluatetheresults.Iftheproblemisnotsolved,returntostep1or2asappropriate.,WhereSystemsAnalystsWork,IntraditionalbusinessesWorkingintraditionalinformationservicesorganizations(permanentprojectteams)Workingincontemporaryinformationservicesorganizations(dynamicprojectteams)InoutsourcingbusinessesContractedtotraditionalbusinessesInconsultingbusinessesContractedtotraditionalbusinessesInapplicationsoftwarebusinessesBuildingsoftwareproductsfortraditionalbusinesses,TraditionalISServicesOrganization,ContemporaryISServicesOrganization,BusinessTrendsandDrivers,Totalqualitymanagement(TQM)Continuousprocessimprovement(CPI)GlobalizationoftheeconomyInformationtechnologyproblemsandopportunitiesYear2000problem(Y2K)EurocurrencydirectiveEnterpriseresourceplanning(ERP)Electroniccommerce(ECorE-commerce),TotalQualityManagement,Totalqualitymanagement(TQM)isacomprehensiveapproachtofacilitatingqualityimprovementsandmanagementwithinabusiness.Informationsystemsqualitystandards:ISO9001,QualitysystemsModelforqualityassuranceindesign/development,production,installation,andservicing.CapabilityMaturityModel(CMM)isaframeworktoassessthematuritylevelofanorganizationsinformationsystemsdevelopmentandmanagementprocessesandproducts.Itconsistsoffivelevelsofmaturityasmeasuredbyasetofguidelinescalledthekeyprocessareas.,TheCMMProcessManagementModel,TheCapabilityMaturityModel(CMM)isaframeworktoassessthematuritylevelofanorganizationsinformationsystemdevelopmentandmanagementprocessesandproducts.Itconsistsoffivelevelsofmaturityasmeasuredbyasetofguidelinescalledthekeyprocessareas.Level1Initial:Systemdevelopmentprojectsfollownoprescribedprocess.Level2Repeatable:Projectmanagementprocessesandpracticesareestablishedtotrackprojectcosts,schedules,andfunctionality.Level3Defined:Astandardsystemdevelopmentprocess(sometimescalleda“methodology”)ispurchasedordeveloped,andintegratedthroughouttheinformationsystems/servicesunitoftheorganization.Level4Managed:Measurablegoalsforqualityandproductivityareestablished.Level5Optimizing:ThestandardizedsystemdevelopmentprocessiscontinuouslymonitoredandimprovedbasedonmeasuresanddataanalysisestablishedinLevel4.,TheCMMProcessManagementModel,BusinessProcessRedesign,Businessprocessredesign(BPR)isthestudy,analysis,andredesignoffundamentalbusinessprocessestoreducecostsand/orimprovevalueaddedtothebusiness.Usuallycomplementedbycontinuousprocessimprovement,ContinuousProcessImprovement,Continuousprocessimprovement(CPI)isthecontinuousmonitoringofbusinessprocessestoeffectsmallbutmeasurableimprovementstocostreductionandvalueadded.Essentiallytheoppositeofbusinessprocessredesign;however,CPIcanandfrequentlydoescomplementBPR.,LegacySystems,Legacysystemsareolderinformationsystemapplicationsthathavebecomecrucialtotheday-to-dayoperationofabusinessandthatmayusetechnologiesconsideredoldoroutdatedbycurrentstandards.Canbeadverselyaffectedbytechnologyandeconomicforces:Year2000EuroCanbereplacedbyalternativesolutions:ERPE-Commerce,EnterpriseResourcePlanning,AnEnterpriseresourceplanning(ERP)softwareproductisafullyintegratedinformationsystemthatspansmostbasicbusinessfunctionsrequiredbyamajorcorporation.AnERPproductisbuiltaroundacommondatabasesharedthesebusinessfunctions.ExamplesofERPsoftwarevendorsinclude.BaanJ.D.EdwardsOraclePeoplesoftSAP,ElectronicCommerce,Electroniccommerce(e-commerceorEC)involvesconductingbothinternalandexternalbusinessovertheInternet,intranets,andextranets.Electroniccommerceincludesthebuyingandsellingofgoodsandservices,thetransferoffunds,andthesimplificationofday-to-daybusinessprocessesallthroughdigitalcommunications.Threebasictypesofelectroniccommerceapplicationsinclude:MarketingBusiness-to-consumer(B2C)Business-to-business(B2B),TheSystemsAnalystasaFacilitator,SkillsRequiredbySystemsAnalysts,WorkingknowledgeofinformationtechnologyComputerprogrammingexperienceandexpertiseGeneralbusinessknowledgeProblem-solvingskillsInterpersonalcommunicationskillsInterpersonalrelationsskillsFlexibilityandadaptabilityCharacterandethicsSystemsanalysisanddesignskills,TheTenCommandmentsofComputerEthics1.Thoushaltnotuseacomputertoharmotherpeople.2.Thoushaltnotinterferewithotherpeoplescomputerwork.3.Thoushaltnotsnooparoundinotherpeoplescomputerfiles.4.Thoushaltnotuseacomputertosteal.5.Thoushaltnotuseacomputertobearfalsewitness.6.Thoushaltnotcopyoruseproprietarysoftwareforwhichyouhavenotpaid.7.Thoushaltnotuseotherpeoplescomputerresourceswithoutauthorizationorpropercompensation.8.Thoushaltnotappropriateotherpeoplesintellectualoutput.9.Thoushaltthinkaboutthesocialconsequencesoftheprogramyouarewritingorthesystemyouaredesigning.10.Thoushaltalwaysuseacomputerinwaysthatinsureconsiderationandrespectforyourfellowhuman,ComputerEthics,Source:ComputerEthicsInstitute,Source:ComputerEthicsInstitute,InformationSystemBuildingBlocks,InformationSystemBuildingBlocks,Whatareinformationsystems,andwhoarethestakeholdersintheinformationsystemsgame?Describethedifferencebetweendataandinformation.Definetheproductcalledaninformationsystem,anddescribetheroleofinformationtechnologyininformationsystems.Differentiatebetweenfront-andback-officeinformationsystems.Describefiveclassesofinformationsystemapplications(transactionprocessing,managementinformation,decisionsupport,expert,andofficeautomationsystems)andhowtheyinteroperate.Describetheroleofinformationsystemsarchitectureinsystemdevelopment.Namesixgroupsofstakeholdersininformationsystemdevelopment.Namethreefocusesforinformationsystems.DescribefourperspectivesoftheDATAfocusforaninformationsystem.DescribefourperspectivesofthePROCESSfocusforaninformationsystem.DescribefourperspectivesoftheINTERFACEfocusforaninformationsystem.DescribetheroleofacomputernetworkasitrelatestoDATA,PROCESSES,andINTERFACES.,BuildingBlocksofAnInformationSystem,DataandInformation,Dataarerawfactsabouttheorganizationanditsbusinesstransactions.Mostdataitemshavelittlemeaningandusebythemselves.Informationisdatathathasbeenrefinedandorganizedbyprocessingandpurposefulintelligence.Thelatter,purposefulintelligence,iscrucialtothedefinitionPeopleprovidethepurposeandtheintelligencethatproducestrueinformation.,InformationSystems),Wptr=eptr;,is-a,wptr,(ErrorWindow*eptr;),eptr,（参照）收信方对象的定义,属性值,操作的规格部分,对象（发信方）,对象（收信方）,可视性（关系）的定义,消息,属性,数据的交互,生成,结合,方法,收信方对象的类,静态结合与动态结合,静态结合：操作的规格部分（消息）与操作的执行部（方法）的结合在编译时进行动态结合：操作的规格部分（消息）与操作的执行部（方法）的结合在程序执行时进行,面向对象分析与设计,什么是面向对象分析与设计面向对象分析的实践面向对象分析与设计中再利用的实践,什么是面向对象分析与设计,面向对象是一种从下到上的思想,面向对象的软件开发,OOA面向对象分析,分析明确问题,OOD面向对象设计,设计决定如何解决问题,OOP面向对象编程,编程根据解决方案实现解决,什么是面向对象分析与设计,面向对象实现软件开发的一贯性,利用面向对象方法的软件开发历程,软件开发的工业化、大众化,分析,设计,编程,设计,编程,编程,上流,下流,开发过程,80年代前,80年代中,80年代后,爱好者研究者,一般SE,面向对象分析阶段,要求模型的构建3种模型的表现分析阶段中的对象,要求文件,要求说明（要求模型）,消除不完整性、模糊、赘长,承担者对问题的理解,模型化,委托方,委托者+承担者,承担者,分析阶段的目的,面向对象分析阶段,代表性的方法论中的3种模型,分析阶段的实例,对象模型的建立动态模型的建立功能模型的建立,accept,abstract,Abstract1,6,7Accept2,4,5,1,文件,行序号,单词,索引,文件索引的制作,分析阶段的实例,初期状态,登录中,项目登录,开始,开始,项目登录,索引印刷,文件,索引,单词,行序号,对象群的静态构造,文件索引制作系统的分析阶段的3种模型,对象的动态动作,项目登录索引印刷,对应表,对象的功能,设计阶段,设计阶段是软件开发的中心部分基本设计和详细设计逻辑设计和物理设计,设计阶段的内容,设计阶段,设计阶段的实例1,索引生成程序的设计为实现追加对象3种模型的扩展（见图：索引生成程序中设计阶段的3种模型）,设计阶段的实例1,单词,文件,行号,过滤器,树,队列,设计阶段的实例2,初期状态,登录中,表示中Do:display,Add/insert,MakeReport,文章,过滤,索引,Tree,Queue,单词,行号,main,输出报告,读取单词,读取行号,打印,下面没有单词,01,索引生成程序中设计阶段的3种模型,对象群的静态构造,对象的动态处理过程,对象的行为功能,设计阶段的实例2,编程分析、设计、编程的连续性,对象（静态）模型,动态模型,功能模型,静态模型,动态模型,功能模型,接口部分,实现部分,OOA,OOD,OOP,从3种模型的分析到编程的流程,编程,设计,分析,整体流程,面向对象的开发过程来回型的开发形态,整体流程,抽象化,U1,问题领域,再利用,要求,OOA,OOD,OOP,面向对象开发过程,现实世界,追加,数据管理,任务管理,计算机,追加,细化,整体流程,来回型开发形态,分析,设计,编程,分析,设计,编程,瀑布型,来回型,原型,原型,各种方法,4大方法的特征,中大规模,小规模,小中规模,小大规模,对象规模,中,高,特别高,低,技术公开度,Rose,OOATool,OMTool,Teamwork,辅助工具,丰富,少,少,丰富（1979-）,适用成绩,1990年,1990年,1991年,1988年,发表年,-,-高,自然高,自然低,分析.设计过程OOD的联结度,扩充了Ada用的方法论的旧Booch法。从HOOD,OOSD等Ada用的方法论的影响大，也受E-R，JSD法的影响高,组合E-R图及ShlaerboolisVisibile;public:show();hide();move(intdirection,intamount);,数据类型,类定义,操作函数群,分析的抽象数据类型和编程的抽象数据类型,面向对象编程,从分析得到的抽象数据的实现,分析,编程,classWindowprivate:intxPos,yPos;boolisVisibile;public:show();hide();move(intdirection,intamount);,分析的封装化和编程的封装化,窗口xposyposisVisibleshow()hide()move(.),分析中的原则：属性隐蔽、操作公开,编程中：private,public关键词指定隐蔽和公开,面向对象编程,从分析得到的继承的实现,分析,编程,classWindowprivate:intxPos,yPos;public:move(.);classResizableWindow:publicWindowprivate:intxSize,ySize;public:resize();,分析的继承和编程的继承,窗口xposyposmove(.),可变窗口xSizeySizeresize(.),is-a,面向对象编程,从分析得到的消息通信的实现,分析,编程,分析的消息通信和编程的消息通信,用户接口,窗口,Show,Hide,Move,classWindowprivate:intxPos,yPos;boolisVisible;public:show();hide();move(intdirectuion,intamount);WindowtheTarget;theTarget.show();theTarget.move();theTarget.hide();,消息通信,面向对象编程,从分析得到的状态的实现,改变状态的处理和不改变状态的处理,确认大小,检查字符串,清空,追加,清空,追加,确认大小,检查字符串,：改变状态的处理,：不改变状态的处理,初期状态,字符串登录状态,存在的4种问题(之一),功能中心的弊病编程-过程语言开发分析设计-以功能为中心把握问题事实：“事物的结构”比“功能”自然分析设计以“事物的结构”为中心并非不是最佳方法而是，用过程语言开发不能实现系统分析vs用户要求产生差异,存在的4种问题(之二),数据与行为分离的弊病过程性语言：数据的访问没有限制程序员：可自由的更新和参照但要求对数据构造全部理解缺乏限制数据变更所进行的处理的范围通过某一特制函数来访问某一重要数据由于没有制约这种违反原则的手段现状是规则不彻底,存在的4种问题(之三),重复开发的弊病费事：不易于扩展已有处理或数据结构仅一部分的修改也得全部拷贝再实施修改，这样就重复具有类似程序的处理或数据。错误难免：因为是复制的，所以原有错误就有可能重复出现出现修改两处同样的错误的现象（因前后没有逻辑关系）,存在的4种问题(之四),利用顺序靠默契的弊病数据和处理是分离的，所以即使是操作同一数据的处理之间，也没有表示他们有联系的手段，也没有表示他们的处理顺序的手段。处理的使用者需推测程序的提供者所想象的利用顺序来利用这些处理为了解决这些问题，出现了面向对象方法,利用过去方法未能解决的问题,利用过去方法未能解决的问题,利用面向对象方法解决,（1）重视编程、功能为主,（2）数据与处理的分离,（3）类似软件的重复开发,（4）利用顺序以默契为前提,（2）封装化,（1）抽象化,（3）继承,（4）状态,基本概念（抽象化）,抽象化功能中心事物中心（不仅解决编程而且整个系统开发问题）OO法：数据+行为=一个对象单位可以记述对象之间消息的传递不是将现实原封不动的表示为对象，而是仅着重问题的重要侧面，或者说是强调所注目的问题的侧面，这就叫抽象化对象就具有了表示数据和操作以及处理什么如何么处理的手段，抽象化是OO的特征之一,EnlargeRotateIsequalShow,面向对象,以前,抽象化,数据+行为,数据+行为,数据+行为,现实,事物中心,现实,事物中心,抽出重要的侧面（性质）,自然的联想,联想的转换,计算机,计算机,系统开发,系统开发,功能中心,事物中心,基本概念（抽象化）,抽象化的效果-把握对象容易化（3个）,功能中心变成事物中心,着眼于事物的构造,仅将重要的侧面模型化,对于变更较安定,自然地表示现实,分析的焦点明确化,具有相同性质的对象再抽象成类（Class）,将类再抽象成抽象的类，这样就可以掌握事物的构造体系了,基本概念（封装）,封装（信息隐蔽）数据与处理的分离数据为中心的处理一体化对象所有的数据从外部是不可视的，仅通过行为才可以对对象数据进行操作。这样的情形比喻成“封装”或叫“信息隐蔽”。见下图示例。,以前,需要的文件在何处放回何处好，用户定,需要的文件在何处放回何处好，由管理人员安排,面向对象,用户（操作）,用户（操作）,文件箱（数据）,文件箱（数据）,管理人