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王林章软件工程组南京大学计算机科学与技术系lzwang@nju.edu.cn?IT现状不同种类的操作系统,应用软件,系统软件和应用基础结构(applicationinfrastructure)相互交织一些现存的应用程序被用来处理当前的业务流程(businessprocesses),因此从头建立一个新的基础环境是不可能的。面临的问题业务的不断变化需要企业做出快速的反应需要复用现有的应用程序和应用基础设施(applicationinfrastructure)为客户,商业伙伴以及供应商提供新的互动渠道ThebusinessdriversforanewapproachWhileITexecutiveshavebeenfacingthechallengeofcuttingcostsmaximizingtheutilizationofexistingtechnologyAtthesametimetheyhavetocontinuouslystrivetoservecustomersbetterbemorecompetitivebemoreresponsivetothebusiness’sstrategicpriorities.Therearetwounderlyingthemesbehindallofthesepressures:HeterogeneityandchangeThebusinessdriversforanewapproachHeterogeneityMostenterprisestodaycontainarangeofdifferentsystems,applications,andarchitecturesofdifferentagesandtechnologies.Integratingproductsfrommultiplevendorsandacrossdifferentplatformswerealmostalwaysanightmare.Butwealsocannotaffordtotakeasingle-vendorapproachtoIT,becauseapplicationsuitesandthesupportinginfrastructurearesoinflexible.ChangeGlobalizationande-businessareacceleratingthepaceofchange.Improvementsintechnologycontinuetoaccelerate,feedingtheincreasedpaceofchangingcustomerrequirements.ThebusinessdriversforanewapproachAsaresult,businessorganizationsareevolvingfromthevertical,isolatedbusinessdivisionsofthe1980’sandearliertothehorizontalbusiness-process-focusedstructuresofthe1980’sand1990’stowardsthenewecosystembusinessparadigm.Businessservicesnowneedtobecomponentizedanddistributed.Thereisafocusontheextendedsupplychain,enablingcustomerandpartneraccesstobusinessservices.ThebusinessdriversforanewapproachQuestions:HowdoImakemyITenvironmentmoreflexibleandresponsivetotheeverchangingbusinessrequirements?Howcanwemakethoseheterogeneoussystemsandapplicationscommunicateasseamlesslyaspossible?Howcanweachievethebusinessobjectivewithoutbankruptingtheenterprise?CurrentlymanyITexecutivesandprofessionalsalikebelievethatnowwearegettingreallyclosetoprovidingasatisfactoryanswerwithservice-orientedarchitecture.ThebusinessdriversforanewapproachInordertoalleviatetheproblemsofheterogeneity,interoperabilityandeverchangingrequirements,suchanarchitectureshouldprovideaplatformforbuildingapplicationserviceswiththefollowingcharacteristics:LooselycoupledLocationtransparentProtocolindependentBasedonsuchaservice-orientedarchitecture,aserviceconsumerdoesnotevenhavetocareaboutaparticularserviceitiscommunicatingwithbecausetheunderlyinginfrastructure,orservice“bus”,willmakeanappropriatechoiceonbehalfoftheconsumer.Theinfrastructurehidesasmanytechnicalitiesaspossiblefromarequestor.ParticularlytechnicalspecificitiesfromdifferentimplementationtechnologiessuchasJ2EEor.NETshouldnotaffecttheSOAusers.Weshouldalsobeabletoreconsiderandsubstitutea“better”serviceimplementationifoneisavailable,andwithbetterqualityofservicecharacteristics.Object-orientedanalysisanddesignObject-orientedanalysisanddesignLarmandescribestheessenceoftheobject-orientedanalysisanddesignasconsidering“aproblemdomainandlogicalsolutionfromtheperspectiveofobjects(things,concepts,orentities)”inApplyingUMLandPatterns–AnIntroductiontoObject-OrientedAnalysisandDesign.Jacobson,etal,definetheseobjectsasbeing“characterizedbyanumberofoperationsandastatethatrememberstheeffectsoftheseoperations”inObject-OrientedSoftwareEngineering:AUseCaseDrivenApproach.Inobject-orientedanalysis,suchobjectsareidentifiedanddescribedintheproblemdomain,whileinobject-orienteddesign,theyaretransitionedintologicalsoftwareobjectsthatwillultimatelybeimplementedinaobject-orientedprogramminglanguage.Withobject-orientedanalysisanddesign,certainaspectsoftheobject(orgroupofobjects)canbeencapsulatedtosimplifytheanalysisofcomplexbusinessscenarios.Certaincharacteristicsoftheobject(s)canalsobeabstractedsothatonlytheimportantoressentialaspectsarecaptured,inordertoreducecomplexity.Component-baseddesignComponent-baseddesignisnotanewtechnology.Itisnaturallyevolvedfromtheobjectparadigm.Packagedsolutionsuitescanalsobeencapsulatedassuch“components”.Oncetheorganizationachievesahigherlevelofarchitecturalmaturitybasedondistinctlyseparatefunctionalcomponents,theapplicationsthatsupportthebusinesscanbepartitionedintoasetofincreasinglylargergrainedcomponents.Componentscanbeseenasthemechanismtopackage,manageandexposeservices.Theycanuseasetoftechnologiesinconcert:Large-grainedenterprisecomponents,thatimplementbusiness-leveluse-cases,canbeimplementedusingnewerobject-orientedsoftwaredevelopmentincombinationwithlegacysystems.Service-orienteddesignInComponent-BasedDevelopmentforEnterpriseSystems,Allenincludesthenotionofservices,describingacomponentas“anexecutableunitofcodethatprovidesphysicalblack-boxencapsulationofrelatedservices.Itsservicecanonlybeaccessedthroughaconsistent,publishedinterfacethatincludesaninteractionstandard.Acomponentmustbecapableofbeingconnectedtoothercomponents(throughacommunicationsinterface)toalargergroup”.Aserviceisgenerallyimplementedasacourse-grained,discoverablesoftwareentitythatexists
本文标题:SA-Style-SOA
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