Table Of ContentLecture Notes in Artificial Intelligence 1760
Subseries ofLectureNotesin ComputerScience
Editedby J.G. Carbonelland J. Siekmann
Lecture Notes in Computer Science
Editedby G.Goos,J. Hartmanisand J.van Leeuwen
3
Berlin
Heidelberg
NewYork
Barcelona
HongKong
London
Milan
Paris
Singapore
Tokyo
John-Jules Ch. Meyer
Pierre-Yves Schobbens (Eds.)
Formal Models
of Agents
ESPRIT Project ModelAge Final Workshop
Selected Papers
1 3
SeriesEditors
JaimeG.Carbonell, CarnegieMellonUniversity,Pittsburgh,PA,USA
Jo¨rgSiekmann, UniversityofSaarland,Saarbru¨cken,Germany
VolumeEditors
John-JulesCh.Meyer
UtrechtUniversity,DepartmentofComputerScience
Padualaan14,DeUithof,3508TBUtrecht,TheNetherlands
E-mail:[email protected]
Pierre-YvesSchobbens
Institutd’Informatique
RueGrandgagnage21,5000Namur,Belgium
E-mail:[email protected]
Cataloging-in-Publicationdataappliedfor
DieDeutscheBibliothek-CIP-Einheitsaufnahme
Formalmodelsofagents:ESPRITprojectModelAgefinalworkshop;selectedpapers/
John-JulesCh.Meyer;Pierre-YvesSchobbens(ed.).-Berlin;Heidelberg;
NewYork;Barcelona;HongKong;London;Milan;Paris;Singapore;
Tokyo:Springer,2000
(Lecturenotesincomputerscience;Vol.1760:Lecturenotesin
artificialintelligence)
ISBN3-540-67027-0
CRSubjectClassification(1998):I.2.11,C.2.4,D.2,F.3,I.2
ISBN3-540-67027-0Springer-VerlagBerlinHeidelbergNewYork
Thisworkissubjecttocopyright.Allrightsarereserved,whetherthewholeorpartofthematerialis
concerned,specificallytherightsoftranslation,reprinting,re-useofillustrations,recitation,broadcasting,
reproductiononmicrofilmsorinanyotherway,andstorageindatabanks.Duplicationofthispublication
orpartsthereofispermittedonlyundertheprovisionsoftheGermanCopyrightLawofSeptember9,1965,
initscurrentversion,andpermissionforusemustalwaysbeobtainedfromSpringer-Verlag.Violationsare
liableforprosecutionundertheGermanCopyrightLaw.
(cid:2)c Springer-VerlagBerlinHeidelberg2000
PrintedinGermany
Typesetting:Camera-readybyauthor
SPIN10719643 06/3142–543210 Printedonacid-freepaper
Preface
This volume contains a number of revised papers that were selected from pa-
pers presented at the last ModelAge workshop held in Certosa di Pertignano
(Italy) in 1997, organised by the Institute of Psychology of the Italian CNR
(IP-CNR), Division of Artificial Intelligence, Cognitive Modeling and Interac-
tion. The organisation chair was held by Amedeo Cesta. The workshop, and
indeed the ModelAge project as a whole, aimed to bring together a number
of researchers stemming from different disciplines to discuss formal models of
agency from different perspectives. These disciplines included artificial intelli-
gence, software engineering, applied logic, databases, and organisation theory.
The field of intelligent agents has become an important research area within
these disciplines, and in the workshop as in the present volume the concept of
agency is thus considered from a multi-disciplinaryperspective.
In the introductory chapter of this volume more can be found on the area
of intelligent agents as well as on the topic of formal models of these. We fur-
thermore provide some key references, so that the reader can better appreciate
the position of the present volume within the literature on agent technology.
Moreover, we briefly describe the ModelAge project which was an ESPRIT-
funded Basic Research WorkingGroup dedicated to the study of formalmodels
of agents, and one may find the details of the organisation of the workshop
here. Finally in this chapter we give a detailed overview of the contents of this
book from which we hope you will get an impression of the deliberately multi-
disciplinaryapproach that is taken.
Finally, we would like to take this opportunity to thank all the persons in-
volved in the realisation of this book: authors, PC members, additional review-
ers,theorganisersandaudienceoftheModelAgeworkshop,andthepeoplefrom
Springer-Verlag.
November 1999 John-Jules Meyer
Pierre-Yves Schobbens
Table of Contents
FormalModels of Agents: An Introduction ..................................1
John-Jules Ch. Meyer and Pierre-Yves Schobbens
A Model of BDI-Agent in Game-Theoretic Framework ......................8
Stanisl(cid:2)aw Ambroszkiewicz and Jan Komar
DynamicBelief Hierarchies ................................................20
John Bell and Zhisheng Huang
ModellingInternal Dynamic Behaviour of BDI Agents .....................36
Frances Brazier, Barbara Dunin-Ke¸plicz, Jan Treur, and Rineke Verbrugge
Towards an Agent-Oriented Framework for Specification of Information
Systems ...................................................................57
Stefan Conrad, Gunter Saake, and Can Tu¨rker
The Impossibilityof Modelling Cooperation in PD-Game ..................74
Rosaria Conte, Cristiano Castelfranchi, and Roberto Pedone
Designing Multi-agent Systems around an Extensible Communication
Abstraction ................................................................90
Enrico Denti and Andrea Omicini
Social Interactions of Autonomous Agents: Private and GlobalViews on
Communication ...........................................................103
Frank Dignum
Towards a Proof-Theoretic Foundation for Actor Specification and
Verification ...............................................................123
Carlos H.C. Duarte
Nondeterministic Actions with Typical Effects: Reasoning about Scenarios 143
Barbara Dunin-Ke¸plicz and Anna Radzikowska
Agents’ DynamicMental Attitudes .......................................157
Bruno Errico
DiagnosticAgents for Distributed Systems ................................173
Peter Fro¨hlich, Iara de Almeida Mo´ra, Wolfgang Nejdl,
and Michael Schroeder
VIII Table of Contents
Preferential Action Semantics (Preliminary Report) .......................187
John-Jules Ch. Meyer and Patrick Doherty
DialecticalProof Theory for Defeasible Argumentation with Defeasible
Priorities (Preliminary Report) ...........................................202
Henry Prakken
The Role of Diagnosis and Decision Theory in Normative Reasoning ......216
Leendert W.N. van der Torre, Pedro Ramos, Jos´e Luiz Fiadeiro,
and Yao-Hua Tan
Contextual Deontic Logic .................................................240
Leendert W.N. van der Torre and Yao-Hua Tan
Author Index ...........................................................253
Formal Models of Agents:
An Introduction
John-Jules Ch. Meyer1 and Pierre-Yves Schobbens2
Intelligent SystemsGroup, Dept.of Computer Science
UtrechtUniversity,P.O. Box 80089, 3508 TB, Utrecht,The Netherlands
[email protected]
Institut d’Informatique, Fac. Univ.Notre-Dame dela Paix
RueGrandgagnage 21, B-5000 Namur, Belgium
1 Intelligent Agents
Althoughinphilosophicalliteraturethenotionofanagentasacognitivesubject
has been aroundfor a long time, in the last decade or so the area of ‘Intelligent
Agents’ has also become a major area of research within artificial intelligence
andcomputerscience,anareawithabigpromiseasthereareamyriadofpossi-
ble applications (see e.g. [4]). As might be expected, within the latter areas the
conceptofanagentgenerallyhasamoretechnicalmeaning,althoughthereisno
generalconsensusonits definition. But mostlyby anagentis meanta(software
or hardware) entity that has some degree of autonomy, which typically comes
down to displaying reactive and/or proactive behaviour (that is to say that the
agentiscapableofreactingtoitsenvironmentandtakinginitiative,independent
ofthe user,respectively),mightpossessreasoningandlearningcapabilities,and
is able to communicate in some intelligent way with other agents. Sometimes
agentsareascribed‘mentalattributes’suchasamentalstatecomprisingknowl-
edge, belief, Whether these mental attributes are merely metaphorical (i.e. a
convenientmeans of describing agents) or ‘real’in the sense that these artificial
agents possess some ‘truly cognitive’ capabilities like human or, to a lesser ex-
tent, animal agents do, is of course a matter of philosophical debate but also a
question depending to a large extent on the application one has in mind.
One view of agents that is very ‘computational’ is that of viewing agents
as the next step in programming as a successor of the popular object-oriented
programming paradigm.Although objects already display some form of ‘auton-
omy’ in the sense that they have their own datatypes and methods which can
be called by other objects, agents are rather to be consideredas ‘subjects’, pos-
sessingtheirownontology(signature),theirownknowledge/beliefsabouttheir
environment (possibly including themselves if they have reflective capabilities)
and their own goals to achieve. Moreover,communicating is much less a matter
ofjustinvokingamethodofanotheragent,butratheraskingquestionsto other
agents which these other agents may (or may not) handle in their own way.
Of course, these matters can also be viewed from a more cognitive perspec-
tive. (Some researchers like to include human agents into their conception of
anagent,andconsider‘mixed’systemsofhumanandartificialagents.)Onecan
J.-J.Ch.Meyer,P.-Y.Schobbens(Eds.):FormalMethodsofAgents,LNAI1760,pp.1–7,1999.
(cid:2)c Springer-VerlagBerlinHeidelberg1999
2 John-Jules Ch. Meyer and Pierre-YvesSchobbens
thenlookatagentsatthe‘micro’level:theirinternalmake-up,possiblydescribed
in terms of mental states (comprising knowledge, beliefs, intentions, etc.), and
at the ‘macro’ level: external and ‘social’ behaviour (including communication,
co-ordination, co-operation).
It is important to stress that the area of intelligent agents is truly multi-
disciplinary. Clearly the area has a big overlap with contemporary AI. Some
feel that agent-based systems are the next generation of the information-based
and knowledge-based(expert) systems from the 80’s. In any case one can read-
ily agree that agent systems are a new generation of intelligent systems, and
as such part of the AI research programme. As we saw above agent-oriented
programming can also be viewed as a new programming paradigm in computer
science, more in general. And, as we have also briefly mentioned, traditionally
thereareinfluencesfrom(analytical)philosophy.Manywritingsby(mostly20th
century)philosophersonthenatureof‘action’arerelevantforthefieldof‘intel-
ligentagents’.Finally,alsocognitiveandsocialscientistsshowagreatinterestin
agents, in particular systems in which multiple agents are present, the so-called
multi-agent systems (MAS). Their interest includes how agent societies develop
and employ norms to govern/ constrain their behaviour.
There has arisen a great deal of literature on the topic of intelligent agents.
Many papers deal with the practical issue of designing and building them for
particular applications such as agents for assisting users of the internet. See,
for example, the Proceedings of the Autonomous Agents and PAAM (Practi-
calApplicationofIntelligentAgentsandMulti-AgentTechnology)Conferences,
where many researchers exchange their views on how to address these appli-
cations. More theoretical are the MAAMAW (e.g. [1]) and ICMAS conferences
on Multi-Agent Systems (e.g. [2]), and particularly the series of books entitled
“Intelligent Agents” in the Springer Lecture Notes in AI [8,10,9,7,5], based on
the proceedings of the ATAL workshops (“Agent Theories, Architectures, and
Languages”).
2 Formal Models
Formalmodelsareatooltoarriveatunambiguousandprecisemeaningsofcon-
cepts. They may comprise a well-defined language with a precise,mathematical
semantics in terms of set theory, for example. Also one may think of some ax-
iomatic system (logic) that lays down the exact meanings of the terms of the
logic by postulates / axioms. Since the field of agents is ‘exploding’ in many
directions, it seems very reasonable to strive for a (common) formal model on
which there is some consensus among the various researchers (stemming from
different disciplines).
However,the needforformalmodelsgoesbeyondthe mereunderstandingof
the subject ofintelligentagents(althoughofcoursethis isveryimportant,too)!
As with traditional software, in order to design and implement agent systems
it would be very advantageous to have some formal means of describing and
specifyingthe behaviourofthesesystems.Forthisreason,too,formalmodelsof
