资源描述:
《the dynamics of probabilistic structural relevance》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、TheDynamicsofProbabilisticStructuralRelevanceL.C.vanderGaag&J.-J.Ch.MeyerUtrechtUniversity,DepartmentofComputerScienceP.O.Box80.089,3508TBUtrecht,TheNetherlandsAbstractProbabilisticinferencewithabeliefnetworkingeneraliscomputationallyex-pensive.Sincetheconceptofst
2、ructuralrelevanceprovidesforidentifyingpartsofabeliefnetworkthatareirrelevanttoacontextofinterest,itallowsforal-leviatingtosomeextentthecomputationalburdenofinference:inferencecanberestrictedtothenetwork'srelevantpart.Thestructurallyrelevantpartofabeliefnetwork,ho
3、wever,isnotstatic.Itmaychangedynamicallyasreasoningprogresses.Weaddressthedynamicsofstructuralrelevanceandintroducetheconceptofanindependenceprojectiontocapturethesedynamics.1IntroductionComplexproblemdomainsthatarefraughtwithuncertaintyareinthefocusofat-tentionof
4、articial-intelligenceresearchandhavebeensoforsometimenow.Oneofthemostpromisingframeworksfordealingwithuncertaintythathaveemergedfromthisresearchistheframeworkof(Bayesian)beliefnetworks[Pearl,1988].Thisframeworkisrmlyrootedinprobabilitytheory.Itprovidesapowerfula
5、ndintuitivelyappealingformalismforrepresentingaprobabilitydistribution;informallyspeaking,abeliefnetworkconsistsofaqualitativepart,encodingadomain'svariablesandtheprobabilisticindependencesamongtheminadirectedgraph,andaquantitativepart,encodingprobabilitiesoverthe
6、sevariables.Inaddition,theframeworkoersasetofalgorithmsforprobabilisticinference.Thebelief-networkframeworkisbecomingin-creasinglypopularforbuildingknowledge-basedsystems,andmoreandmorereal-lifeapplicationsemployingtheframeworkarebeingrealised.Asapplicationsofthe
7、belief-networkframeworkgrowlarger,thenetworksinvolvedincreaseinsizeaccordingly.Forlargebeliefnetworks,probabilisticinferenceshowsatendencytobecomerathertime-consuming.SinceprobabilisticinferenceisknowntobeNP-hard[Cooper,1990],thistendencymaynotbedeniedingeneral.In
8、manyreal-lifeproblemdomains,however,reasoningwithabeliefnetworkconcentratesononlysomevariablesofinterest.Inamedicaldiagnosticapplication,forexample,them