Anthill A Framework for the Development of Agent-B

Anthill:AFrameworkfortheDevelopmentofAgent-BasedPeer-to-PeerSystems¨OzalpBabaogluHeinMelingAlbertoMontresorTechnicalReportUBLCS-2001-09November2001(RevisedSeptember2002)DepartmentofComputerScienceUniversityofBolognaMuraAnteoZamboni740127Bologna(Italy)TheUniversityofBolognaDepartmentofComputerScienceResearchTechnicalReportsareavailableingzippedPostScriptformatviaanonymousFTPfromtheareaftp.cs.unibo.it:/pub/TR/[e-mail][e-mail]TechnicalReportSeries2001-2Formalization,AnalysisandPrototypingofMobileCodeSystems(Ph.D.Thesis),Mascolo,C.,Janaury2001.2001-3Nature-InspiredSearchTechniquesforCombinatorialOptimizationProblems(Ph.D.Thesis),Rossi,C.,Janaury2001.2001-4Desktop3dInterfacesforInternetUsers:EfciencyandUsabilityIssues(Ph.D.Thesis),Pittarello,F.,Jan-uary2001.2001-5AnExpertSystemfortheEvaluationofEDSSinMultipleSclerosis,Gaspari,M.,Roveda,G.,Scandellari,C.,Stecchi,S.,February2001.2001-6ProbabilisticInformationFlowinaProcessAlgebra,Aldini,A.,April2001(RevisedSeptember2001).2001-7ArchitectingSoftwareSystemswithProcessAlgebras,Bernardo,M.,Ciancarini,P.,Donatiello,L.,July2001.2001-8Non-determinisminProbabilisticTimedSystemswithGeneralDistributions,Aldini,A.,Bravetti,M.,July2001.2001-9Anthill:AFrameworkfortheDevelopmentofAgent-BasedPeer-to-PeerSystems,Babaoglu,O.,Meling,H.,Montresor,A.,November2001(RevisedSeptember2002).2002-1ATimedJoinCalculus,B¨unzli,D.C.,Laneve,C.,February2002.2002-2AProcessAlgebraicApproachfortheAnalysisofProbabilisticNon-interference,Aldini,A.,Bravetti,M.,Gorrieri,R.,March2002.2002-3QualityofServiceandResources`OptimizationinWirelessNetworkswithMobileHosts(Ph.DThesis),Bononi,L.,March2002.2002-4SpecicationandAnalysisofStochasticReal-TimeSystems(Ph.D.Thesis),Bravetti,M.,March2002.2002-5QoS-AdaptiveMiddlewareServices(Ph.D.Thesis),Ghini,V.,March2002.2002-6TowardsaSemanticWebforFormalMathematics(Ph.D.Thesis),Schena,I.,March2002.2002-7RevisitingInteractiveMarkovChains,Bravetti,M.,June2002.2002-8UserUntraceabilityintheNext-GenerationInternet:aProposal,Tortonesi,M.,Davoli,R.,August2002.2002-9TowardsAdaptive,ResilientandSelf-OrganizingPeer-to-PeerSystems,Montresor,A.,Meling,H.,Babaoglu,O.,September2002.2002-10TowardsSelf-Organizing,Self-RepairingandResilientLarge-ScaleDistributedSystems,Montresor,A.,Babaoglu,O.,Meling,H.,September2002.2002-11Messor:Load-BalancingthroughaSwarmofAutonomousAgents,Montresor,A.,Meling,H.,Babaoglu,O.,September2002.Anthill:AFrameworkfortheDevelopmentofAgent-BasedPeer-to-PeerSystems¨OzalpBabaoglu1HeinMeling2AlbertoMontresor1TechnicalReportUBLCS-2001-09November2001(RevisedSeptember2002)AbstractRecentpeer-to-peer(P2P)systemsarecharacterizedbydecentralizedcontrol,largescaleandextremedynamismoftheiroperatingenvironment.Assuch,theycanbeseenasinstancesofcomplexadaptivesystems(CAS)typicallyfoundinbiologicalandsocialsciences.InthispaperwedescribeAnthill,aframe-worktosupportthedesign,implementationandevaluationofP2Papplicationsbasedonideassuchasmulti-agentandevolutionaryprogrammingborrowedfromCAS.AnAnthillsystemconsistsofadynamicnetworkofpeernodes;societiesofadaptiveagentstravelthroughthisnetwork,interactingwithnodesandcooperatingwithotheragentsinordertosolvecomplexproblems.AnthillcanbeusedtoconstructdifferentclassesofP2Pservicesthatexhibitresilience,adaptationandself-organizationproperties.WealsodescribepreliminaryexperienceswithAnthillinimplementingalesharingapplication..DepartmentofComputerScience,UniversityofBologna,MuraAnteoZamboni7,40127Bologna(Italy),Email:babaoglu,[e-mail],NorwegianUniversityofScienceandTechnology,O.S.Bragstadsplass2A,N-7491Trond-heim(Norway),Email:[e-mail]11Introduction1IntroductionInformally,peer-to-peer(P2P)systemsaredistributedsystemsbasedontheconceptofresourcesharingbydirectexchangebetweenpeernodes(i.e.,nodeshavingthesameroleandresponsibil-ity).Exchangedresourcesincludecontent,asinpopularP2Plesharingapplications[17,8,10],andstoragecapacityorCPUcycles,asincomputationalandstoragegridsystems[1,16,9].DistributedcomputingwasintendedtobesynonymouswithP2Pcomputinglongbeforethetermwasinvented,butthisinitialdesirewassubvertedbytheadventofclient-servercomputingpopularizedbytheWorldWideWeb.ThemodernuseofthetermP2Panddistributedcomputingasintendedbyitspioneers,however,differsinseveralimportantaspects.First,P2PapplicationsreachouttoharnesstheouteredgesoftheInternetandconsequentlyinvolvescalesthatwerepreviouslyunimaginable.Second,P2Pbydenition,excludesanyformofcentralizedstructure,requiringcontroltobecompletelydecentralized.Finally,andmostimportantly,theenviron-mentsinwhichP2Papplicationsaredeployedexhibitextremedynamisminstructure,contentandload.Thetopologyofthesystemtypicallychangesrapidlyduetonodesvoluntarilycomingandgoingorduetoinvoluntaryeventssuchascrashesandpartitio