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LectureVAgent-OrientedSoftwareEngineeringJohnMylopoulosUniversityofOttawaFederalUniversityofPernambuco(UFPE),Recife,November20,2019

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…AnIdea...  SoftwareEngineeringmethodologieshavetraditionallycomeabout in a “late-to-early” phase (or, “downstream-to-upstream”)fashion.

  In particular, Structured Programming preceded (andinfluenced!) Structured Analysis and Design; likewise,Object-Oriented Programming preceded Object-OrientedDesignandAnalysis.

  In both cases, programming concepts were projectedupstreamtodictatehowdesignsandrequirementsaretobeconceived.Whatwouldhappenifweprojectedrequirementsconcepts

downstreamtodefinesoftwaredesignsandevenimplementations?

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Whatissoftware?An engineering artifact, designed, tested and deployedusing engineeringmethods; rely heavily on testing andinspectionforvalidation(Engineeringperspective)A mathematical abstraction, a theory, which can beanalyzedforconsistencyandcanberefinedintoamorespecializedtheory(Mathematicalperspective)A non-human agent, with its own personality andbehavior, defined by its past history and structuralmakeup(CogSciperspective)Asocialstructureofsoftwareagents,whocommunicate,negotiate,collaborateandcooperatetofulfiltheirgoals(Socialperspective)

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Whyagent-orientedsoftware?  Next generation software engineering will have to supportopen, dynamic architectures where components canaccomplishtasksinavarietyofoperatingenvironments.

  Consider application areas such as eBusiness,web services,pervasiveand/orP2Pcomputing.

  These all call for software components that find andcompose services dynamically, establish/drop partnershipswithothercomponentsandoperateunderabroadrangeofconditions.

  Learning, planning, communication, negotiation, andexception handling become essential features for suchsoftwarecomponents.

☛ ... agents!

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Agent-orientedsoftwareengineering  Manyresearchershavebeenworkingonitfor~20years.  Researchonthetopic:

  Extend UML to support agent communication,negotiationetc.(e.g.,[Bauer99,Odell00]);  Extend current agent programming platforms (e.g.,JACK) to support not just programmingbut alsodesignactivities[Jennings00].

  Weproposed the Troposmethodology for building agent-orientedsoftware;themethodologysupportsrequirementsanalysis,aswellasdesign.

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Whatisanagent?

  Aperson,anorganization,certainkindsofsoftware.  A software agent has beliefs, goals (desires), intentions,hencetheyhaveaBDIarchitecture.

  Agentsaresituated,autonomous,flexible,andsocial.  Butnote:human/organizationalagentscan’tbeprescribed,theycanonlybepartiallydescribed.

  Softwareagents,on theotherhand,have tobecompletelyprescribedduringimplementation.

  Beliefs correspond to (object) state, intentions constitute arun-time concept (an agent’s agenda). For design-time, theinterestingnewconceptagentshavethatobjectsdon’thaveisthatof‘goal’.

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TheTroposMethodology  We propose a set of primitive concepts, as in i*, and amethodologyforagent-orientedrequirementsanalysisanddesign.

  Wewanttocoverfourphasesofsoftwaredevelopment:ü  Early requirements -- identifies stakeholders and theirgoals;

ü  Laterequirements--introducesystemasanotheractorwhichcanaccommodatesomeofthesegoals;

ü  Architectural design -- more system actors are addedandareassignedresponsibilities;

ü  Detaileddesign--completesthespecificationofsystemactors.

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Earlyreq’nts:Stakeholderandtheirgoals

Asocialsettingconsistsofactors,eachhavinggoals(and/orsoftgoals)tobefulfilled.

Participant Manager

Schedulemeeting

Productivemeetings

Schedulemeeting

Low costscheduling

Good meeting

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LateRequirementswithi*

AttendMtg

UsefulMtg

CalendarInfo

SuitableTime

SchedulerParticipant

ScheduleMtgSystem

Timetablemanager

Reporter

ManageCalendarInfo

MtgInfo

ContributeToMtg Initiator

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Softwarearchitectureswithi*

CalendarInfo

Timetablemanager

Reporter

CollectCalendarInfo

RetrieveMtgInfo

UpdateMtgInfo

Processquery

Updater

Retriever

InfoGatherer

System

Participant

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TheTroposdevelopmentprocess  Initialization: Identify stakeholder actors and their goals,placetheminSandGrespectively;

  Step:ForeachgoalginGwantedbyainS:ü  Actoraadoptsg;ü  ActoradelegatesgtoanexistingactorinS;ü  Actoradelegatesittoanewactora’;a’isaddedtoS;ü  Refinegintonewsubgoalsg1,…,gn;addthesetoG;ü  Declaregoalg“denied”.

  Terminationcondition:Allinitialgoalshavebeenfulfilled,assumingallactorsdeliverontheircommitments.

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TroposcomparedtoOOtechniques  Goal refinement extends functional decompositiontechniques,inthesensethatitexploresalternatives.

  Actor dependency graphs extend object interactiondiagrams inthatadependency is intentional,needstobemonitored, may be discarded, and can be established atdesign-orrun-time.

  In general, an actor architecture is open and dynamic;evolvesthroughnegotiation,matchmakingandlike-mindedmechanisms.

  Thedistinctionbetweendesignandrun-timeisblurred.  Soistheboundarybetweenasystemanditsenvironment(softwareorotherwise.)

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Whyisthisbetter(…sometimes…)  Traditionally, goals (and softgoals) are operationalizedand/ormetricizedbeforelaterequirements.

  This means that a solution to a goal is frozen into asoftware design early on and the designer has to workwithintheconfinesofthatsolution.

  This won’t do in situations where the operationalenvironmentofasystem,includingitsstakeholders,keepschanging.

  This won’t do either for software that needs toaccommodate a broad range of users, with differentcultural, educational and linguistic backgrounds, or userswithspecialneedsleadingtoever-changingrequirements.

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Thetaleoftwodesigns

Controller

Interface

Display(“Please see Smith tomorrow morning at 9am”)

Communicate(mtg062)

Interface

Controller

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FormalTropos

  EachconceptinaTroposdiagramcanbedefinedformally,intermsofatemporallogicinspiredbyKAOS.

  Actors, goals, actions, entities, relationships aredescribedstaticallyanddynamically.

Customer

InsuranceCompanyPremium

payment

Repairscovered

Claimspayout

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AFormalTroposexample

EntityClaimHasclaimId:Number,insP:InsPolicy,claimDate,date:Date,details:Text

NecessarydatebeforeinsP.expDateNecessary(∀x)(Claim(x)∧●¬Claim(x)⟹¬RunsOK(x.insP.car))endClaim

ActionMakeRepairPerformedbyBodyShopRefinesRepairCarInputcl:ClaimPre¬RunsOK(cl.insP.car)PostRunsOK(cl.insP.car)...

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Agoaldependencyexample

GoalDependencyCoverRepairsModeFulfillDependerCustomerDependeeInsuranceCoHascl:ClaimDefined/*theamountpaidoutbytheinsurancecompany

coversrepaircosts*/endCoverRepairs

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AnalysingTroposmodels  ModelsinSEareusedforanalysishumancommunication;  But, this is not enough! Large models can be hard tounderstand,ortakeseriously!

  We need analysis techniqueswhich offer evidence that amodelmakessense:ü  Simulation through model checking, to explore thepropertiesofgoals,entities,etc.overtheirlifetime;

ü  Goalanalysiswhichdeterminethefulfillmentofagoal,giveninformationaboutrelatedgoals;

ü  Socialanalysiswhichlooksatviability,workability,…foraconfigurationofsocialdependencies.

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ModelcheckingforTropos  Define an automatic translation from Formal Troposspecificationstothe input languageofthenuSMVmodelchecker[Cimatti99].

  Veri f icat ion of temporal propert ies of staterepresentationsoffiniteTroposmodels.

  Discovery of interesting scenarios that representcounterexamples to properties not satisfied by thespecifications.

  Modelsimulation.

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MappingTropostonuSMV  The language supported by a model checker includesvariables that can takeoneof a finitenumberof values.Also, constraints on the allowable transitions from onevaluetoanother.

  HowdowemapFormalTropostonuSMV?ü  Eachgoalinstanceisrepresentedbyavariablethatcantake values “no”, “created”, “fulfilled”; theserepresentthepossiblestatesofagoalinstance.

ü  EachactionisrepresentedbyaBooleanvariablethatistrueonlyatthetimeinstancewhentheactionoccurs.

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TranslationforCoverRepairsVARCoverRepairs:{no,created,fulfilled}INITCoverRepairs=noTRANSCoverRepairs=no->(next(CoverRepairs)=no|

next(CoverRepairs)=created)TRANSCoverRepairs=created->(next(CoverRepairs)=

created|next(CoverRepairs)=fulfilled)TRANSCoverRepairs=fulfilled->next(CoverRepairs)=fulfilledTRANSCoverRepairs=no->next(CoverRepairs=created->!RunOK)

TRANSCoverRepairs=created->next(CoverRepairs=fulfilled->DamageCosts=fulfilled)

TRANSCoverRepairs=created->next(CoverRepairs=fulfilled<->RunsOK)

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FromnuSMVspecstoFSMs  FiniteStateMachineforCoverRepairs(cl)

no created fulfilled

!RunsOK(cl.insP.car)DamageCosts(cl)=fulfilled

RunsOK(cl.insP.car)Necessaryconditionfortransition Necessaryand

sufficientconditionfortransition

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Modelchecking  AmodelconsistsofafinitesetofFSMs,eachrepresentingan instance of a class in the Tropos model (goal,dependency, entity, …), or a propositional variable (e.g.,RunsOK(cl.insP.car)).

  A simulation considers all possible simulations of theseFSMs,takingintoaccountinter-FSMconstraints.

  Even though the space of possible simulations is infinite,onlyafinite(butusuallylarge!)numberofthesematters.

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AnInterestingpropertyLTLSPECF[CoverRepairs(cl)=fulfilled->MakeRepair(cl.insP.car)]“If/whensometimeinthefutureCoverRepairs(cl)isfulfilled,

then(atthattime)MakeRepairs(cl.insP.car)istrue”Thispropertydoesnotholdforthemodel.Acounterexampleis:

Variable t1 t2 t3 t4RunsO K false false tr ue tr ue

DamageCosts no no created fulf i l led

Cover Repair s no cr eated created fulf i l led

M akeRepair false false false false

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AfixAddtothedefinitionoftheentityclassCar…Necessary¬RunsOK(self)∧¬MakeRepair(self)⇒❍¬RunsOK(self)...

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ExperimentswiththeT-ToolTropos models can have an unbounded number ofinstances; to make model checking work, we pickincreasinglylargermodels(e.g.,1,2,...instancesperclass)andcheckwhetherapropertywewanttoproveleadstocounter-examples.

  Howdowepickmodels?Howdoweknowwhentostop?  Experiments to demonstrate the scalability of theapproach.

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Otherthreadsofresearch  [Security] Extend Tropos to support ‘ownership’,‘permission’ and ‘trust’; this leads tomodels where youcancheckthateveryactorhasthepermissionssheneedstocarryoutherobligations[Zannone05]èPhDthesisbyNicolaZannone(Trento,2007).

  [Risk Management] Extend the risk managementframework [Feather05] to allow goal-based risk analysisèPhDthesisbyYudisAsnar(Trento,2009).

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UML,Catalysis&Co.

Relatedwork

KAOSZ

AUML

TROPOSGAIA

!!TheGAP!!

i* JACK

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Conclusions  We have proposed a set of concepts and sketched amethodology that together support Agent-OrientedSoftwareDevelopment.

  Agent-Oriented Software Development has been an up-and-coming paradigm for more than 20 years, thanks totheriseandever-growingdemandforsocialsoftware.

  Thisisalong-termproject,andmuchremainstobedone.

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References  [Bauer99]Bauer,B.,ExtendingUMLfortheSpecificationofAgentInteractionProtocols.OMGdocumentad/99-12-03.

  [Castro02]Castro,J.,Kolp,M.,Mylopoulos,J.,“TowardsRequirements-DrivenSoftwareDevelopmentMethodology:TheTroposProject,” InformationSystems27(2),PergamonPress,June2002,365-389.

  [Chung00]Chung, L.,Nixon,B.,Yu,E.,Mylopoulos, J.,Non-FunctionalRequirements inSoftwareEngineering,KluwerPublishing,2000.

  [Dardenne93] Dardenne, A., van Lamsweerde, A. and Fickas, S., “Goal–directedRequirementsAcquisition”,ScienceofComputerProgramming,20,1993.

  [Fuxman01a]Fuxman,A.,Pistore,M.,Mylopoulos,J.andTraverso,P.,“ModelCheckingEarly Requirements Specifications in Tropos”, Proceedings Fifth International IEEESymposiumonRequirementsEngineering,Toronto,August2001.

  [Fuxman01b]Fuxman,A.,Giorgini,P.,Kolp,M.,Mylopoulos,J.,“InformationSystemsasSocialOrganizations”, Proceedings International Conference on FormalOntologies forInformationSystems,OgunquitMaine,October2001.

  [Iglesias98] Iglesias, C., Garrijo, M. and Gonzalez, J., “A Survey of Agent-OrientedMethodologies”,Proceedingsof the5th InternationalWorkshopon IntelligentAgents:AgentTheories,Architectures,andLanguages(ATAL-98),Paris,France,July1998.

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References(cont’d)  [Jennings00]Jennings,N.“OnAgent-BasedSoftwareEngineering”,Artificiallntelligence117,2000.

  [Mylopoulos92]Mylopoulos,J.,Chung,L.andNixon,B.,"RepresentingandUsingNon-Functional Requirements: A Process-Oriented Approach," IEEE Transactions onSoftwareEngineering18(6),June1992,483-497.

  [Odell00] Odell, J., Van Dyke Parunak, H. and Bernhard, B., “Representing AgentInteraction Protocols in UML”, Proceedings 1st International Workshop on Agent-OrientedSoftwareEngineering(AOSE00),Limerick,June2000.

  [Wooldridge00]Wooldridge, M., Jennings,N., andKinny,D.,“TheGaiaMethodologyfor Agent-Oriented Analysis and Design,” Journal of Autonomous Agents and Multi-AgentSystems,3(3),2000,285–312.

  [Yu95]Yu,E.,ModellingStrategicRelationshipsforProcessReengineering,Ph.D.thesis,DepartmentofComputerScience,UniversityofToronto,1995.

  [Zambonelli00] Zambonelli, F., Jennings, N., Omicini, A., andWooldridge,M.,“Agent-OrientedSoftwareEngineeringforInternetApplications,”inOmicini,A.,Zambonelli,F.,Klusch, M., and Tolks-Dorf R., (editors), Coordination of Internet Agents: Models,Technologies,andApplications,Springer-VerlagLNCS,2000,326–346.