Agent-OrientedModelingwith
GraphTransformation
RalphDepkeReikoHeckelJochenMalteK¨uster
Dept.ofComputerScience,UniversityofPaderbornWarburgerStr.100,D-33098Paderborn
{depke,reiko,jkuester}@uni-paderborn.de
Abstract.Theagentparadigmcanbeseenasanextensionofthenotionof(ac-tive)objectsbyconceptslikeautonomy,cooperation,andgoal-orientedbehavior.Mainstreamobject-orientedmodelingtechniquesdonotaccountfortheseagent-specificaspects.Therefore,dedicatedtechniquesforagent-orientedmodelingarerequiredwhicharebasedontheconceptsandnotationsofobject-orientedmod-elingandextendtheseinordertosupportagent-specificconcepts.Inthispaper,anagent-orientedmodelingtechniqueisintroducedwhichisbasedonUMLnotation.Graphtransformationisusedbothonthelevelofmodelinginordertocaptureagent-specificaspectsandastheunderlyingformalsemanticsoftheapproach.
1Introduction
Asconceptsandtechnologiesofagent-basedsystemsbecomepartofmoretraditional
software,agent-basedsoftwaredevelopmentisabouttobecomeoneaspectofmain-
streamsoftwareengineering.Today,mostsoftwaresystemsareimplementedinan
object-orientedprogramminglanguagelikeC++orJava,andtheanalysisanddesign
ofsuchsystemsisbasedonobject-orientedmodelinglanguagesliketheUML[16].
Thus,inordertoincorporateagentconceptsintomainstreamsoftwaredevelopment,an
integratedmodelingapproachforobject-andagent-basedsystemsisrequired.
Asmodelingconcepts,agentsandobjectshavecomplementaryroles:agentsact
autonomously,drivenbytheirgoalsandplans,therebysensingandreactingtotheir
environmentandcooperatingwithotheragents.Objectsencapsulatedatastructures
andoperationsandprovideservicestootherobjects.Inthissense,Jennings,etal.
[15]statethat“Thereisafundamentalmismatchbetweentheconceptsusedbyobject-
orienteddevelopers...andtheagentview.”However,theviewofobjectsasmereser-
viceprovidershasitsoriginsintheparadigmsofsequentialOOprogramming,andis
nolongeradequatewhenconsideringconcurrentlanguageslikeJava.Asamodeling
abstractionforconcurrentobjects,theconceptofactiveobjecthasbeenestablished
[16]whichhasmuchsimilaritywiththeagentparadigm.Whatisstillmissingevenin
activeobjectsistheideaofgoal-drivenbehaviororproactivityofagentsandtherelated
conceptofautonomy.Autonomyemphasizesthefactthatanagenthascontrolaboutits
ResearchsupportedbytheESPRITWorkingGroupAPPLIGRAPH.operations:theyarenotcalledfromoutsidelikemethodsbutareonlyinvokedbythe
agentitselfinordertoreachacertaingoal.
Still,object-orientedmodelinglanguagesliketheUMLprovideagoodbasisfor
themodelingofagent-basedsystems.Infact,anumberofauthorsproposeextensions
andadaptionsofobject-orientedmodelinglanguagesforagent-basedsystems[12,21,
20].MostapproachessufferfromaproblemwhichisalsoencounteredinOOmodeling
languages:thelackofadequatemeansfordescribingthesemanticsofoperations,their
pre-conditionsandeffectsonthesystem’sconfiguration.Inparticular,thesemanticsof
operationsisrelevantforthemodelingofreactivebehavior,i.e.,forthewayhowagents
senseandmodifytheirenvironment.
BuildinguponthenotationoftheUML[16],inthispaperwepresentanagent-
orientedmodelingtechniquewhichemploysgraphtransformationrules1forspecifying
theeffectoftheagents’operations.Wepayspecialattentiontothemodelingofco-
operationandautonomy.Graphtransformationrulesinrequirementspecificationand
analysisallowustocapturethecooperationamongseveralagentsresultinginajoint
activity.Inthedesignphase,graphtransformationrulesspecifytheeffectoftheagents’
localoperations.Here,thenon-determinisminherenttoarule-basedapproachprovides
aconvenientmodelfortheautonomyofagents.Asunderlyingformalframework,typed
graphtransformationsystems[2]provideanaturalintegrationofstructuralanddynamic
aspectsaswellaselaborateconceptsfordefiningtheconsistencybetweenrequirements
specification,analysis,anddesign(see[4]).
Next,weshalldiscussinmoredetailtherelevantpropertiesofagent-basedsystems
aswellasthemainconceptsofourmodelingapproach.Thefollowingsections3to
5areconcernedwiththethreemainphasesofsoftwaremodeling(i.e.,requirements
specification,analysis,anddesign).Section6reviewsanddiscussesconceptsofroles
inobject-andagent-orientedmodeling,andSection7concludesthepaper.
Thepapercontinuespreviousworkonagent-basedsystemswhichisdocumented
in[3,5,14].
2Agent-OrientedModeling
InthisSection,weoutlineourapproachtoagent-orientedmodeling.First,wediscuss
typicalaspectsofagent-basedsystemslikereactivity,autonomy,proactivity,andcoop-
eration,anddescribehowtheseaspectsarecapturedinourapproach.Then,wesurvey
thethreemainphasesofsystemmodeling,i.e.,requirementspecification,analysis,and
designandexplainhowthisgeneralpatternisinstantiatedinourcase.
Althoughitisdifficulttofindageneral(technical)definitionofthetermagent,
someimportantcharacteristicsofagentscanbeidentifiedwhichdistinguishthemfrom
programsorobjects[10].Reactivityisthecapabilityofanagenttoperceiveitsenvi-
ronmentandreacttochanges.Thispropertycanbeconsideredasaprerequisitefor
purposefulautonomyofagents,anditisalreadycapturedwithintheconceptofactive
objects.Inourapproach,agentsperceivetheirenvironmentbymatchingtheleft-hand
1See,e.g.,[17,6,7]forarecentcollectionofsurveysand[1]foranintroductorytext.
