Specification and Verification of Multi-agent Systems

416 Pages·2010·7.95 MB·English

by  N. Alechina

Specification and Verification
of Multi-agent Systems

· ·
Mehdi Dastani Koen V. Hindriks
John-Jules Charles Meyer
Editors
Specification and Verification
of Multi-agent Systems
Foreword by
Wiebe van der Hoek
123
Editors
MehdiDastani KoenV.Hindriks
UtrechtUniversity DelftUniversityofTechnology
Dept.Information&Computing Mekelweg4
Sciences 2628CDDelft
Padualaan14 TheNetherlands
3584CHUtrecht [email protected]
TheNetherlands
[email protected]
John-JulesCh.Meyer
UtrechtUniversity
Dept.Information&Computer
Sciences
Padualaan14
3584CHUtrecht
TheNetherlands
[email protected]
ISBN978-1-4419-6983-5 e-ISBN978-1-4419-6984-2
DOI10.1007/978-1-4419-6984-2
SpringerNewYorkDordrechtHeidelbergLondon
LibraryofCongressControlNumber:2010930883
(cid:2)c SpringerScience+BusinessMedia,LLC2010
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Foreword
In the last decade, multi-agent systems have both become widely applied and also
increasingly complex. The applications include the use of agents as automous de-
cision makers in often safety-critical, dangerous, or high impact scenarios (traffic
control,autonomoussatellites,computationalmarkets).Thecomplexityarisesfrom
thefactthatnotonlydoweexpecttheagenttomakedecisionsinsituationsthatare
notanticipatedatforehand,theagentalsointeractswithothercomplexagents,with
humans,organisations,anditlivesinadynamicenvironment(activatorsofanagent
canfail,communicationispronetoerror,humanresponsemaybeambiguous,rules
ofanorganisationmayleavebehaviouropenorover-constrained,andenvironments
maychange‘spontaneously’orasaresultofotheragentsactinguponit).
TakingthesetwofactstogethercallforarigorousSpecificationandVerification
ofMulti-AgentSystems.Sinceintelligentagentsarecomputationalsystems,itisno
wonder that this activity builds upon and extends concepts and ideas of specify-
ingandverifyingcomputer-basedsystemsingeneral.Forone,anaxiomisthatthe
toolsaremainlylogical,orinanycaseformal.Butalthoughtraditionaltechniques
ofspecificationandverificationgoalongwaywhenreasoningaboutthecorrectness
ofasingleagent,thereareadditionalquestionsalreadytobeaskedatthislevel:do
we‘only’requiretheagenttobehavewellunderapre-definedsetofinputs,ordo
wewanttoallowfor(partially)undefinedscenarios?Anddowecareaboutthe‘cor-
rectness’ofanagent’sbeliefs,desiresandintentionsduringacomputation?Howdo
wewanttoguaranteethattheagent‘knowswhatheisdoing’,has‘reasonablede-
sires’and‘onlydropsanintentionifit(sgoal)isfulfilled,orcannotbereasonably
be fulfilled any longer’? And a predecessor of this ‘how to guarantee’ question is
equallyimportant:whatdoweexactlymeanbythoserequirements?
Inamulti-agentsystem,specificationandverificationbecomesonlyharderand,
indeed,moreinteresting.Oncewehaveanunderstandingofhowtomaketheagents
behavecorrectlyindividually,isthispropertythenalsocompositional,inthesense
that it applies to the system as a whole? What are the requirements we need to
impose on the interaction among the agents, the ability of the human users, the
organisationtheagentsrepresent,ortheenvironmentasawhole,inordertomake
v
vi Foreword
the multi-agent system behave as required? If we have means to specify this, then
howdowecheckthis?
Thisbook,withcontributionsfrommanyworld-leadingauthorsinthefield,gives
manyanswerstothequestionsabove,therebyindeed often generalising ideasthat
havebeenaroundinthespecificationandverificationcommunity.Forinstance,the
bookaddressestheoremproving(‘allimplementations,ormodels,ofthespecifica-
tionverify’)asameanstoverifypropertiesofcognitiveagents,refinement(making
sure the runs of a system are in a desired class) as a compositional means to de-
rivecorrectimplementationsfromagivenspecification,andmodelchecking(‘does
thisparticularimplementationverify’)asatechniquetoverifycertainmulti-agent
systembehaviour.Modelcheckingisappliedtoagentcommunication,topractical
agentprogramminglanguages,andtolanguagesinwhichagentgoalsplayamajor
role:acomplexitystudyofmodelcheckingfortemporalandstrategiclogicscom-
plements these applications. There is also a chapter proposing a hybrid approach
which guarantees on the one hand that some desirable properties in the specifica-
tionlanguagearemetbyanyimplementationintheagentprogramminglanguage,
andon topof that,adebugging frameworkthatchecks fortemporaland cognitive
assertions.
Thebookalsohaschaptersthatfocusonspecificationlanguages,forinstancea
cognitiveagentspecificationlanguagewithdeclarativeandproceduralcomponents,
andatemporaltracelanguagetoexpressdynamicpropertiesofmulti-agentsystems.
Another chapter advocates to use one (term rewriting) language and its tools for
prototyping,verifyingandtestingagentprograms.
If one takes the autonomy of agents to the extreme, one should leave it to the
agents to act in a correct way. Indeed, this book has a chapter where norms are
used as a way to specify correct, or desired behaviour, and to make sure that the
agents comply with the norm, a game-theoretic framework is proposed. Although
all chapters mentioned above comply with the maxim of formality, there is also a
chapterthatchallengesthisaxiom,andclaimsthatformalverificationforassurance
ofagentsystemsis,onitsown,notenough.
MehdiDastani,KoenHindriksandJohn-JulesMeyerarewell-choseneditorsof
this book. The work of their Intelligent Systems group in Utrecht (now also con-
tinued in the Man Machine Interaction group in Delft by Koen) encompasses all
aspectsthisbookaddresses:theirlonghistoryofinvolvementinverifactionofpro-
grams,theirearlyworkoriginatinginmodallogicsforspecificationofagents,their
hands-on experience with implementing agents in 3APL and its successors, and
theirinvolvement,fromitsearlydays,informalapproachestonormativesystems,
makesthembettersuitedtocomposethisvolumethananybodyelse.
January2010,Liverpool,UK WiebevanderHoek
Contents
1 UsingTheoremProvingtoVerifyPropertiesofAgentPrograms..... 1
N.Alechina,M.Dastani,F.Khan,B.Logan,andJ.-J.Ch.Meyer
1.1 Introduction.............................................. 2
1.2 AnAgentProgrammingLanguage........................... 3
1.2.1 SimpleAPL ...................................... 3
1.2.2 SimpleAPLsyntax ................................ 6
1.3 OperationalSemantics ..................................... 6
1.3.1 Non-interleavedexecution .......................... 8
1.3.2 Interleavedexecution .............................. 9
1.4 Logic ................................................... 11
1.4.1 Preliminary....................................... 11
1.4.2 Language ........................................ 11
1.4.3 Semantics........................................ 12
1.4.4 Axiomatisation ................................... 13
1.5 Verification .............................................. 16
1.5.1 Expressingthenon-interleavedstrategy ............... 17
1.5.2 Expressingtheinterleavedstrategy ................... 19
1.6 Exampleofusingtheoremprovingtoverifypropertiesofan
agentprogram ............................................ 24
1.7 RelatedWork............................................. 26
1.8 Conclusion............................................... 27
1.9 Appendix:EncodingsofpropertiesinMSPASS................ 28
1.9.1 MSPASSencodingoftheexample ................... 28
1.9.2 MSPASSencodingofalemmafortheproofofthe
blind commitment property of thevacuumcleaneragent 30
1.9.3 -encodingoftheblindcommittmentproperty 32
vii
viii Contents
2 TheRefinementofMulti-AgentSystems .......................... 35
L.As¸tefa˘noaeiandF.S.deBoer
2.1 Introduction.............................................. 36
2.1.1 RelatedWorks .................................... 38
2.2 FromSpecificationtoImplementationAgentLanguages......... 39
2.2.1 Preliminaries ..................................... 39
2.2.2 FormalisingMentalStatesandBasicActions .......... 39
2.2.3 BUnityAgents.................................... 41
2.2.4 WhyBUnityAgentsNeedJustice.................... 43
2.2.5 BUpLAgents..................................... 44
2.2.6 WhyBUpLAgentsNeedCompassion ................ 46
2.2.7 AppraisingGoals.................................. 47
2.3 TheRefinementofIndividualAgents......................... 48
2.4 TowardsMulti-AgentSystems .............................. 52
2.4.1 Action-basedChoreographies ....................... 53
2.4.2 AFinerNotionofRefinement ....................... 54
2.5 TimingExtensionsofMAS................................. 58
2.5.1 AddingTimetoBUnity ............................ 59
2.5.2 AddingTimetoBUpL ............................. 61
2.5.3 AShortNoteonTimedRefinement .................. 62
2.6 Conclusion............................................... 64
3 ModelCheckingAgentCommunication .......................... 67
J.Bentahar,J.-J.Ch.Meyer,andW.Wan
3.1 Introduction.............................................. 68
3.2 BriefOverviewofModelCheckingMulti-AgentSystems ....... 70
3.2.1 ExtendingandAdaptingExistingModelCheckers...... 70
3.2.2 DevelopingNewAlgorithmsandTools ............... 72
3.3 Tableau-basedModelCheckingDialogueGames............... 74
3.4 ACTL*Logic ............................................ 74
3.4.1 Syntax........................................... 74
3.4.2 Semantics........................................ 76
3.4.3 TableauRules .................................... 78
3.5 DialogueGameProtocolsasTransitionSystems ............... 80
3.6 VerificationofDialogueGameProtocols...................... 82
Contents ix
3.6.1 AlternatingBu¨chiTableauAutomata(ABTA)forACTL* 82
3.6.2 TranslatingACTL*intoABTA(Step1)............... 83
3.6.3 RunofanABTAonaTransitionSystem(Step2)....... 84
3.6.4 ModelCheckingAlgorithm(Step3).................. 90
3.7 CaseStudies ............................................. 93
3.7.1 VerifyingPNAWS............................... 93
3.7.2 VerifyingNetBill.................................. 99
3.8 DiscussionandFutureWork ................................101
4 DirectionsforAgentModelChecking ............................103
R.H.Bordini,L.A.Dennis,B.Farwer,andM.Fisher
4.1 Introduction..............................................104
4.1.1 AgentsandRationalAgents.........................104
4.1.2 LogicalAgentDescriptions .........................105
4.1.3 FormalVerificationandModelChecking..............106
4.1.4 ProgramVerification...............................108
4.1.5 AgentProgrammingLanguages .....................108
4.2 OurApproach ............................................109
4.2.1 AIL:MappingAgentLanguagestoaCommonBasis....111
4.2.2 AJPF:SpecialisingtheAILandJPFtoworktogether ...112
4.2.3 CurrentStatus ....................................114
4.3 Obstacles ................................................114
4.3.1 Performance......................................114
4.3.2 TargetAgentLanguages............................115
4.3.3 UsingAgentModelChecking .......................116
4.3.4 Applicability .....................................116
4.4 Directions ...............................................116
4.4.1 Applicability:AutonomousandAutonomicSystems ....117
4.4.2 Efficiency:PotentialforuseofMJI...................117
4.4.3 Efficiency: Potential for use of Program
Slicing/Abstraction ................................118
4.4.4 Generality:TargetLanguages .......................119
4.4.5 Engineering:AgentDevelopmentApproach ...........119
4.4.6 Extension:VerificationofGroupsandOrganisations ....120
4.4.7 Applicability:VerifyingHuman-AgentTeamwork ......121
4.4.8 Efficiency/Extension:AlternativeModelCheckers ......122
4.5 ConcludingRemarks ......................................122