《etri之基本网系统》PPT课件

工作流基本技术,2,MainContents,PetriNetNetElementaryNetSystem,3,HistoryofPetrinet,CarlAdamPetri(1962,PhDthesis)InsixtiesandseventiesfocusmainlyontheorySinceeightiesalsofocusontoolsandapplications(cf.CPNworkbyKurtJensen),4,WhyPetriNet?,ThechiefattractionoftheareaofPetriNetisthewayinwhichthebasicaspectsofdistributedsystemsareidentifiedbothconceptuallyandmathematicallyG.ROZENBURGLeidenUniversity,TheNetherlands,5,MainContents,PetriNetNetElementaryNetSystem,6,7,8,DefinitionofNet,ANetisatripleN=(S,T,F)STandST=F(ST)(TS)dom(F)cod(F)=STdom(F)=x|y:(x,y)Fcod(F)=x|y:(y,x)F,SNSBS-elementsofNTNTET-elementsofNXNelementsofNFNFFflowrelationofN,9,NotationsinPetriNet,CalledconditionsinElementaryNetSystemCalledplacesinPlace/TransitionSystem,CalledeventsinElementaryNetSystemCalledtransitionsinPlace/TransitionSystem,10,ANetExample,N=(B,E,F)B=s0,s9E=t1,t8F=(s1,t1),(s0,t1),(s0,t2),(s2,t2),(t5,s1),(t8,s0),(t7,s2),11,CaseandStep,Case(情态）Distributed(global)stateSetofconditionsholdingconcurrentlyConstellation(条件丛)E.g.s0,s1,s9Step(步)Distributed(global)transitionSetofeventsoccurringconcurrentlyE.g.t1,t8,12,pre-SetF),xX;xx=，其中X=STSimplenet(简单网）对于网N(S,T;F),若x,yX,x=yx=y则x=y，其中X=ST,14,KeyQuestions,Whencanastepoccur(concurrently)atacase?WhatistheresultingcasewhenastepoccursatacaseStructuraltransitionrelationrelatingpotentialcasestopotentialcasesviapotentialsteps,15,Question1,Q:WhencananeventeoccuratacaseC?A:ecanoccuratCallpre-conditionsholdatC(eC)andnopost-conditionsholdatC(eC=)记作，CeNEnabled可实施的/有发生权的/受权的,16,Question1(c1),NotethatifCeNthenee=Henceweoftenconsideronlypurenets,17,Question2,Q:WhatistheresultofaneventeoccurringatacaseC?A:WheneoccursatCthepre-conditionsofeceasetoholdandthepost-conditionsofebegintohold;theremainingpartofthecaseremainsunaffected.(HencetheresultingcaseCis(Ce)e)记作，CeNCFiring实施/发生,18,Question2(c1),N=(B,E,F),C,CB,eECeNCiffC-C=e&C-C=ee=eeistheextensionofe,19,Question3,N=(B,E,F),CB,uEQ:WhencantheeventsinuoccurconcurrentlyatC?(whencanthestepuoccuratC)A:ucanoccuratCifftheeventsinucanindividuallyoccuratCwithoutinterferingwitheachother记作，CuN,20,Question4,N=(B,E,F),CB,uE,uisenabledtooccuratCQ:WhatistheresultofuoccurringatC?A:TheresultisthesumoftheresultsoftheeventsinuoccurringindividuallyatC(C=(C-u)u)记作，CuNC,21,Question4(c1),N=(B,E,F),CB,uEuisindependent,indN(u),iff(e1,e2)uife1e2then(e1e1)(e2e2)=UisastepenabledatC,CuN,iffindN(u),uCanduC=,22,Question4(c2),Theorem(diamondproperty)N=(B,E,F),C,DB,uELetu1,u2beapartitionofu(u1,u2,u1u2=,u1u2=u)IfCuND,thenQBsuchthatCu1NQandQu2ND,23,Question5,N=(B,E,F),CB,=e1e2enE+Q:WhencanoccuratC?A:canoccuratCifftheeventsincanindividuallyoccurintheorderdeterminedby记作，CN,24,Question5(c1),THEOREMN=(B,E,F),CB,e1,e2EIfCe1,e2NandCe2N,thenCe1,e2N,25,Question5(c2),THEOREM(sequentializationproperty)N=(B,E,F),C,DB,uE(1)IfCuNifforderinge1,enu,Ce1,enN(2)IfCuNDifforderinge1,enu,Ce1,enND,26,MainContents,PetriNetNetElementaryNetSystem,27,DefinitionofENSystem,AnElementaryNetSystem(ENsystem)isa4-tupleN=(B,E,F,Cin)where(B,E,F)isanetcalledtheunderlyingnetofN,und(N),CinBistheinitialcaseofN,inc(N)NotationsofENsystemBNENFNCN=CinthesetofcasesofNUN=uE:(C1,C2)CNC1uNC2thesetofstepsofN,28,ENSystem,ENsystemasanabstractmodelofadistributedsystem:N=(B,E,F,Cin)GraphicalnotationforanENsystemconsistsofthemarkingofCinbytokens,UnderlyingStaticStructure,DynamicBehaviour,29,30,Relationof2Events,LetNbeanENsystem,letCCN,andlete1,e2EN.e1,e2canberelatedtoeachotheratCin(atleast)threewayssequence,conflict,concurrency,31,Relationof2Events:Sequence,LetNbeanENsystem,letCCN,andlete1,e2EN.e1canoccuratCbutnote2.However,aftere1hasoccurrede2canoccur.e1,e2areinsequenceatCiffCe1,Ce2,andCe2,whereCe1C,32,Relationof2Events:Choice,LetNbeanENsystem,letCCN,andlete1,e2EN.e1ande2canoccurindividuallyatC,buttheycannotoccurtogetheratC.e1,e2isnotastepatC.whethere1ore2willoccuratCisleftunspecified,thusNexhibitsnon-determinism.e1,e2areinconflictatCiffCe1,Ce2,andCe1,e2,33,Relationof2Events:Concurrency,LetNbeanENsystem,letCCN,andlete1,e2EN.e1ande2canoccuratCwitho