emergent social rationality in a peer-to-peer

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1、EmergentSocialRationalityinaPeer-to-PeerSystemAndreaMarcozziandDavidHalesDepartmentofComputerScience,UniversityofBologna,MuraAnteoZamboni7,40127Bologna,Italy{marcozzi,hales}@cs.unibo.it1IntroductionFormanyapplicationspeer-to-peer(P2P)systemsrequiretheirmembernodes(oragents)t

2、obehaveinasociallybeneficial(non-egotistical)way.KalenkaandJennings[4]termedthisrequirementasthePrincipleofSocialRatio-nality:ifanagenthasachoiceofactionsitshouldchosetheactionthatmaximizesthesocialutility(sumofallagentutilitiesinthesystem).Thisprinciplecanbecontrastedwithcla

3、ssicalindividualrationalitythatstatesagentsshouldselectactionsthatmaximizetheirindividualutility.However,developingprotocolsforrealisticP2Psystemsthatadheretotheprincipleofsocialrationalityisverydifficultandpotentiallysocostlyastonegatethebenefits.ThisisbecauseP2Psystemshavenoc

4、entralcontrol,arepo-tentiallyhuge(composedofmillionsofnodes)andhavehighnodeturnover(withuserscontinuallyenteringandleavingthesystem).Inaddition,selfishormaliciousnodescangetintothesystemviahackedclientprograms.Thesefactorsmeanthatindividualnodes,eveniftheywishtofollowasociall

5、yra-tionalprinciple,oftenwillnothaveenoughinformationtogaugetheeffectsoftheiractionsonothers.Recently,simplelocallyadaptiveprotocolshavebeenproposedthatclaimtoproducesociallyrationaloutcomesthroughaprocessofself-organisationeventhoughnodesonlyactontheirownutilityvalues.Inthis

6、approachnodespreferentiallycopyothernodes(byduplicatingtheirbe-haviourandlinks)thathavehigherutilities.However,inthesepreviousworksonlyspecificscenariosareconsideredinwhichcertainplausibleutilityvaluesareselected.Inthispaperweintroduceavariant(ResourceWorld)ofonesuchexistingP

7、2Pscenario[1](SkillWorld).Forbothmodelsweexploredalargespaceofdifferentcost/benefitvaluestocheckiftheprotocolsmaximizedthecollectiveutilityornot.InResourceWorldwefoundthatifthecollectivecostofanactionwaslessthanorequaltothecollectivebenefittheprotocolself-organizedthenetworktoa

8、statewherenodesselectedthisaction.ForSkillWorldwefoundalesssociallyrational