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ID:51091472
大小:531.00 KB
页数:39页
时间:2020-03-18
《嵌入式系统设计 实验三.ppt》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、DesignforModifiabilityQualityAttributes&TacticsModifiabilityScenariosinPractice(1)ModifiabilityisaboutthecostofchangeTimeMoneyTwomajorconcerns:Whatcanchange?ThefunctionthesystemcomputesTheplatformitexistson(portability)QualitiesofthesystemCapacityofthesystemM
2、odifiabilityScenariosinPractice(2)Implementation(sourcecode)ArchitectCompile(compilingoptions)Execution(parametersetting)Build(libraries)Systemconfiguration(parametersetting)DeveloperAdministratorUserSystemdesignWhenisthechangemadeandwhomakesit?Onceachangehas
3、beenspecified,thenewimplementationmustbedesigned,implemented,tested,anddeployed.ModifiabilityGeneralScenario(1)SourceofstimulusEnduserSystemadministratorDeveloper…Stimulus:changestobemadeFunctionsQualityattributesCapacities…ArtifactAnyaspectofasystemModifiabi
4、lityGeneralScenario(2)EnvironmentDesign,compile,buildtimeInitiationtimeRuntimeResponseMake,testanddeploythechangeResponseTimeandmoneyNumberofelementsaffectedModifiabilityTactics(1)Goals:controllingthetimeandcosttoimplement,test,anddeploychanges.TacticstoContr
5、olModifiabilityChangeArrivesChangesmadeChangestestedChangesdeployedwithinbudgetModifiabilityTactics(2)MajorapproachesLocalizemodificationsReducingthenumberofmodulesdirectlyaffectedbyachangePreventtherippleeffectLimitingmodificationstothelocalizedmodulesDeferb
6、indingtimeControllingdeploymenttimeandcostLocalizeModificationsGeneralrule(eventhoughnotprecise):fewercomponentstochangelessmodificationcostTheprimarygoalofthistacticcategoryistoassignfunctionalitytomodulessothatanticipatedchangeswillbelimitedinscopeMaintain
7、semanticcoherenceAnticipateexpectedchangesGeneralizethemoduleLimitpossibleoptionsMaintainSemanticCoherenceSemanticcoherence:therelationshipsamongresponsibilitiesinamodule.Keepthingsthatarerelatedtogether.ChoosingresponsibilitiesthathavesemanticcoherenceAbstra
8、ctcommonservicesKeepaservicerequiredbymultipleclientsinoneplaceModificationsneednotbemadeseparatelyAlsopreventsrippleeffectsE.g.MiddlewareAnticipateExpectedChangesKeepthingsthatarelikelyt
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