文献翻译----基于代理的分布式应用发展的技术

本科毕业设计外文文献及译文文献、资料题目：TechnologiesfortheDevelopmentofAgent-basedDistributedApplications文献、资料来源：期刊文献、资料发表（出版）日期：2008.3.12院（部）：专业：班级：姓名：学号：指导教师：翻译日期：-1-外文文献：TechnologiesfortheDevelopmentofAgent-basedDistributedApplicationsMobileagentcomputingisanextensionoftheearlierideaofprocessmigration.Mobileagenttechnologyoffersseveralpotentialbenefitsoverconventionalclient-servercomputingthatcouldhelpimproveclassicdistributedsystemsdesigns,whichareusuallybasedonthewell-knownremoteprocedurecall(RPC)oritsobject-orientedequivalent,remotemethodinvocation(RMI).Mobilesoftwareagentsenableashiftinthecommunicationsparadigmofdistributedsystemsfromwhatiscalleddatashippingtofunctionshipping.KeytothisshiftisthehigherlevelofabstractionthatamobilesoftwareagentcanprovidecomparedtoaRPCoraRMIcallbecauseitscodeisautonomous.Thisautonomyshouldtheoreticallyreducenetworkloadandcommunicationoverheadindistributedapplicationsaswellasfacilitatethedevelopmentofapplicationsforpotentiallyunreliable,networkedcomputingenvironments.Furthermore,andperhapsevenmoreimportantly,awidespreadagent-enabledinfrastructureprovidesacommonplatformfordistributedapplicationsofarbitrarypurpose.ConsiderthePostScriptexamplegivenbyChess,Harrison,andKershenbaumtoillustratetheadvantagesastandardizedmobileagentexecutionenvironmentoffers.PostScriptdocumentsareprogramsexecutedbyaPostScriptinterpreterandsenttoprintserversthatonlyacceptpassiveinputtext,e.g.,MicrosoftWordfiles.Thedrawbackofthelattermethodisobvious:foreverynewdocumentformat,allprintserversintheworldwouldhavetobeupdated.Theexampleiseasilytransferredtomobileagentcomputing:mobileagentsasageneral-purposecomputingplatformdonotrequireanyspecificfunctionstobeimplementedintheservers,suchasfull-textretrievalmethodsordatabaseinterfaces.DistributedapplicationsbasedonRPC-liketechniquesmightnotbeeasytoadapttolarge-scale,heterogeneous,andpotentiallyunreliableenvironments,liketheInternet,becauseimplementationofRPC-stylesemanticsreliesonrelativelystaticandreliablesystemstructures.Combiningmobileagenttechnologywithwell-establishedmechanismsmightpotentiallyleadtosystemsmuchbettersuitedtotheneedsofInternet-likecomputingenvironments.-2-Tobeabletoclearlydistinguishwhatinthiscontextisreferredtoasconventionalclient-servertechnologyfrommobileagenttechnology,sometermsneedfirstbedefined.AgentAsdefinedbytheObjectManagementGroup(OMG),anorganizationthatdevelopsstandardsforcomponent-basedsoftwaresystems,anagentisacomputerprogramthatactsautonomouslyonbehalfofapersonororganization.MobileAgentAmobileagentisanobjectthatisnotboundtothesystemwhereitbeginsexecution.Ithastheuniqueabilitytotransportitselffromonesystemwithinanetworktoanother.PlaceAplaceisacontextwhereanagentcanexecute..Furthermore,thetermsagentplatformandagentsystemwillbeusedsynonymouslyaccordingtotheOMGdefinition:Anagentsystemisaplatformthatcancreate,interpret,execute,transfer,andterminateagents.Likeanagent,anagentsystemisassociatedwithanauthoritythatidentifiesthepersonororganizationforwhomtheagentsystemacts.Becausemobileagenttechnologyisageneral-purposecomputingplatform,ithasbeencalledasolutioninsearchofaproblem.Inthefollowing,wewillexaminetheadvantagesthatsuchaplatformoffersfordistributedandparallelcomputingandtheproblemsthatpreventitswidespreadsuccess.Subsequently,abriefoverviewofstate-of-the-artagentsystemsisprovided,togetherwithanexaminationofhowthesesystemsaddressthecontinuingchallengesofmobileagentcomputing.MobileagentsasadesignparadigmfordistributedsystemsTheconceptoftransmittingexecutableprogramsbetweenpotentiallyheterogeneousexecutionenvironmentsintroducesanewparadigmfortheimplementationofdistributedapplicationsforlarge-scale,potentiallyunreliable,networkedenvironments.Intraditionalclient-serversystemsthatuseonlyRPC,thedatatobemanipulated,suchastext,relationaldata,andimages,ismovedbetweenproceduresalreadyresidingontheclientandtheserver.Agent-basedcomputing,however,facilitatesthetransportationoftheprocedureitself(thatis,thealgorithmtobeapplied)totheclientbymeansofamobileagent,whichcanleadtolesstraffic.Alsointeresting,isthepossibilityofimplementingdynamicapplicationprogramming-3-interfaces(API)overagentsthroughtheuseofanagentcommunicationlanguage;suchalanguagehasbeenproposedbytheFoundationforIntelligentPhysicalAgents(FIPA).Suchcapabilitywouldallowpossibleintroductionandremovalofservicesthatneednotbefullyspecifiedaprioriineithertheclientortheserver.CharacteristicsofmobileagentsystemsWhatattributesuniquelydistinguishthemobileagentideafromotherdistributedcomputingconcepts?Thereisnoagreedupondefinitiontodate;however,therearekeycharacteristicsofmobileagentsystemsthatfacilitateadvantagesinthedevelopmentofdistributedsystems.MobilityMobility—themostimportantattributeofmobileagents—describestheabilitytomovefromoneexecutionenvironmenttoanother.Forexample,themobilityconceptenablescodetomovetothelocationwherethedataithastoworkwitharelocated,thustakingadvantageoflocalinteraction.Inthefollowing,thetermmobilitywillbeusedtorefertoamobileagent'sabilitytorelocateitselftoanotherplace.AutonomyAutono