From: AAAI Technical Report FS-01-03. Compilation copyright © 2001, AAAI (www.aaai.org). All rights reserved.
A Negotiation Formal Model for Cooperating Agents
Ahmed Hadj Kacem and Mohamed Jmaiel
Universityof S fax
LARISLaboratory
B.E1088, 3018Sfax, Tunisia
E-mail: Ahmed@fsegs.
rnu. tn, Mohamed.Jmaiel@enis.
rnu. tn
Abstract
Theworkpresentedin this paperconstitutesa part of a
globalapproach
aimingat definingthe theoreticalfoundations of a platformfor designingandimplementing
Multi-Agents
Systems.This paperis primarily centeredaroundthe studyof the negotiationas a technique
neededto supportthe cooperativeactivity withinthis
kindof systems.Ourcontributionis mainlyaboutthe
definitionof formalmodels
for negotiationandnegotiating agent.Thesemodelsenableto specifythe relations between
the conceptsof plans, planproposalsand
resourceallocations,on the onehand,andconceptsof
roles, knowledge,
beliefsandcapabilities,onthe other
hand.
Introduction
Multi-Agent Systems(MAS)are designed and implemented
with a set of agents whichinteract accordingto diversified
cooperationmodes,in order to enrich the collective behaviors (Wooldridge& Jennings 1995, Smith & Davis 1980).
Thenegotiation plays a fundamentalrole in the cooperative
activity by enablingthe agentsto solve conflicts whichcould
obstruct such behaviors. Durfee et al. (Durfee & Lesser
1989) define the negotiation as a process whichenhancing
the agreementson the agents’ points of view, by reducing
inconsistencies and uncertainties. This is reached by exchangingrelevant information. Also, Park et al. (Park
Birmingham1995) describe the negotiation as a sequence
of interactive communications
whichare necessaryto solve
conflicts betweenagents. In general, the negotiationis considered as a mechanism
neededto coordinate the actions of
an agent groupduring the problem-solvingprocess.
Thenegotiation has been dealt with in several research
works.Mtiller (Mailer1996)classified these researchesinto
three categories. Thefirst oneconcernsthe studies on negotiation languages. Theyare interested in the communication
primitives, their semanticsas well as the protocols monitoring their occurrenceduring negotiation process. Thesecond
one includes researches on the negotiation decisions. These
worksare interested in algorithms needed to comparenegotiation subjects, utility functions, andagentspreferences.
Researches,in the third category, deal with the negotiation
119
process at high level of abstraction. Theyare mainlyinterested in semanticand behavioralaspects of the negotiation
activity.
Ourcontribution presented in this paper belongs to the
third category. It mainly concerns the study of negotiation as a technique, supportingcooperativeactivity within
MAS.Ourinvestigation aims at suggesting an adequateformal definition in terms of modelsfor negotiation and negotiating agents. Thestudy presentedin this paperis an extension of a previous workdefining formal modelsfor cooperation and cooperating agents (Hadj-Kacem&Jmaiel 1999;
Jmaiel &Hadj-Kacem
2000). In our opinion, such a formal
definition is essential due to the lack of standardsand unified definitions of conceptslike cooperationandnegotiation.
Moreover,
it is not clear at all howthis conceptsare related
to each other. Ourcontribution attempts to identify these
conceptsand to highlight their relations. Oncesucha definition has beenestablished, wecan consideredit as a basis for
defining behavioral aspects of cooperatingand negotiating
agents. In this way,wewill be able to analysetheir behavior.
At a higherlevel this allows to formallyspecify behaviorof
a MAS
and consequently to reason about it. These models
constitute a basis of a specification languagefor cooperating and negotiating agents. Our worksbelong to a global
approachaimingat defining a platform for designing, in a
formal manner, MAS.
In order to define a modelfor negotiation, we proposeto
highlight the links betweenthe concepts of plan, plan proposal, resource allocation, and commitment.
Theseconcepts
wouldbe treated from the points of view of agent group
and individual agent as well. This enabled us to reformulate the conceptsof role and modeof cooperationspecified
in (Jmaiel & Hadj-Kacem
2000).
Concerningthe modelfor negotiating agents, wepropose
to determine the relations betweenthe concepts of knowledge, belief and capability. Theseconceptsallow us to define the mentalstate of a negotiating agent. Moreover,we
insist on the various properties of this kind of agents, such
as autonomy,communication,proposal and evaluation.
This paper is organized in three sections. Thefirst one
presents the various approachesof negotiation within MAS.
The secondone summarizesthe mainconcepts used to highlight the modelsof negotiation and negotiating agent. The
last one presents a formalizationof the suggestedmodels.
State of the Art
Different negotiation techniques have been developed.
Thesetechniquesare generally basedon the rich diversity of
the humannegotiations in various contexts (Davis &Smith
1983). Oneof the moststudied techniquesis basedon an organisational metaphor(Ferber 1995; Davis &Smith 1983).
MainlyIt deals with contract-net whichwasone of the most
used techniques for MAS.This technique allows to coordinate the collective activities of the agentsby establishing
contracts. The same approach has been adopted by Cammarata et al. (S. Cammarata&Steeb 1983). They developednegotiationprotocols to solve conflicts on action plans
betweenagents whichoperate according to various cooperation strategies.
In the context of our study, we attempt to approachthe
negotiation from the point of view of behavioral modelsfor
negotiating agents. In the literature, wedistinguish twomajor tendencies. Accordingto the first one, the negotiation
arises as beingan inherited part of the solution generation
process (Lander &Lesser 1993). It consists of specifying
the proposals of solution componentsmadeby the agents
until a completesolution has been reached. In order to implement the corresponding algorithm, the authors propose
seven operators: Initiate Solution operatorgenerates a proposal whichwill be evaluated by others using the Critique
Solution operator. Thegeneration of a feedback, in a conflict situation, is ensuredby the operatorExtendSolution. If
the conflict persists, the RelaxedRequirement
Solution operator allows, amongothers, the reassessmentof the existing
solution. Theoperators Blind-Receive-Informationand Retrieve Informationensure an access to the knowledgebase.
Theoperator TerminateSearchis used to indicate the endof
the resolution.
Thesecondapproachconsiders the negotiation as a mechanismwhichis independentof the solution generation process. It first consists of decomposing
the initial probleminto
a set of sub-problemswhichwill be distributed amongthe
cooperating agents. Eachagent proceedsto plan its tasks
and to be committedwith others, in order to achieve them.
In this context, the authors in (Park &Birmingham
1995)
proposea generic structure aimingat supportingthe variety
of the negotiationsituations. This structure consists of three
models: negotiating agent model,negotiation languageand
protocol. Thefirst modelpoints out the need for maintaining, for each agent, a mentalstate andits associated operations. It tries to specify the behaviorof agents based on
their beliefs, knowledge,
plans and preferences. Thenegotiation languagedefines a set of performativessuch as: Propose, Counter-Propose,
Ack, Accept, Reject, Retract, FeedBack. Theprotocol of negotiation controls the interactions
betweenagents during the negotiation process.
Negotiation Concepts
In our approach, we makeuse of the notion of the model
in order to determinethe conceptsrelated to the negotiation
within MAS.Thus, we contribute to the design of the negotiation process by specifying two models,namely:
¯ the modelof negotiation, whichis madeup of three levels:
120
global plan, local plan andresourceallocation.
¯ the modelof negotiating agent specifies the internal concepts of an agent as well as their mainproperties.
Negotiation Model
Theprocess of negotiation enables to avoid any potential
conflict situation. Sucha mechanism
is based on the generation of proposals, their evaluation and commitment
in the
case of agreement.Wedistinguish three types of proposals,
namely:
¯ proposalfor realization plan of a global goal,
¯ proposalto be responsiblefor a local goal,
¯ proposalfor time interval to access to a sharedresource.
Eachproposal will be evaluated by every negotiating agent
whoanswers whether with:
¯ an acceptanceif the proposalis accepted,
¯ a rejection if the proposalis rejected and no others are
made,
¯ or a counter-proposalif the proposal is rejected and an
another proposalis generated.
After reachingan agreementbetweenthe agents about a proposal, a commitment
will be taken to ensure its realization.
There are three types of commitments
correspondingto the
proposals presented above.
In the following, wepresent, in an abstract way,the concepts neededfor the qualification of a negotiation activity.
Thisqualification is structuredin three levels: global plan,
local plan andresourceallocation.
¯ A global plan is a decompositionof a global goal in an
orderedset of local goals.
- GlobalPlan Proposalis a suggestion of a global plan
madeby an agent participating in the realization of the
global goal.
- Global Plan Commitment
is an engagementto realize a
global plan acceptedby all agents.
¯ Local Plangathers the various local goals whichconstitute the agentrole after negotiation.
- Local GoalProposalis a suggestionof an agent to take
responsibilityto achievea set of local goals.
- Local Goal Commitmentis described by the assignmentof the local goals to the appropriateagents.
¯ ResourceAllocation relates to allocation of resources
shared betweenagents.
- Interval Proposalis a suggestionof a time interval to
accessto a shared resource.
- Interval Commitmentis an engagementto reserve a
time interval to access to a shared resource during the
local goal realization.
Negotiating agent model
The negotiating agent model expresses the individual aspects of an agent, maintainingcoherencewith the proposed
negotiation model. Suchan agent is characterized by its
mentalstate whichis the result of the interactions with its
environment.This mentalstate plays the role of a regulator,
whichdirects its behavior.So, certain properties characterize a negotiating agent such as communication,autonomy,
reasoning, evaluation, etc. A description of these aspects,
namelymental state and properties of negotiating agent, is
presentedin a detailed way.
¯ MentalState is a set of beliefs, knowledge,
plans and capabilities.
- Beliefs are informationreportedby an external event or
by another agent. Theydescribe the state of the world
from the view point of an agent, and thus, the wayin
whichit perceivesits environment.
- Knowledgegathers information relating to the tasks
achievedby the agent as well as those concerningits
environmentand the other agents. Theydiffer frombeliefs by their degreeof certainty.
- Planis the set of plans on whichthe agent is engaged
to achieve. Theseplans can be of three types, namely:
global plan, modeand local plan.
- Capabilitydescribesthe ability of an agent to carry out
domaintasks as well as control tasks.
¯ Propertiesdescribe the essential properties of an agent,
in order to be able to negotiate. Suchan agent should
be able to propose, to evaluate and to take decisions. In
addition, a negotiating agent mustbe able to adapt its activities withinits environment,
so that it couldagree with
the other agents andcould solve the consideredconflicts.
- Autonomyis an agent directed by tendencies deduced
from its mental state and not by commandscoming
fromthe user or anotheragent.
- Proposingis an agent able to proposeplans for the realization of global goals, local goals andresourceallocation.
- Evaluatingis an agent able to evaluate proposals made
by other agents and to answer by an acceptance or a
rejection accordingto its reasoning.
- Communicating
is characterized by its capabilities to
send, receive and analyse messages.
Thefollowingsection presents these two modelsin a formal
way.
Formal definition of negotiation
This section proposesa formal definition of each concept,
mentionedin the previoussection, and the relations between
them, as well. This formalization, whichis based on a set
language,enables to highlight the type of operationsof the
different conceptscharacterizingthe negotiation.
In our approach,the negotiation processis carried out in
three stages. A first stage consists of proposingglobal plans
decomposing
a common
objective into a set of global goals.
This stage ends with a total acceptanceof a proposalby all
121
the agents. Oncea commitment
on a global plan was made,
the agents start the secondstage of negotiation whichends
after distributing local goalson the different agents. Thelast
stage aims at avoiding conflicts betweenagents.during the
problemresolution by coordinatingthe access on the shared
resources.
Formal model for negotiation
In this modelwesupposethe existence of the three following
sets:
¯ A~is a set of all agents;
¯ BGis a set of all global goals;
¯ B£is a set of all local goals.
A modelof negotiation is defined by a couple (A9, Oc) such
as:
Ag d~j {A1,A2.....
An}
where AiCJtG and n:>l
Theset Agdenotes the agents society.
Oc dof {Bgl, By2,...,
(l<i_<n)
Bgm}
where BgIEB~ and m_>l (l_<i_<m)
The set Oc denotes the commongoal which is madeup of
set of global goals.
Apart from the modelof negotiation, whichformsthe basis for the formaldefinition of the negotiation,wealso need
the followingconcepts andnotations:
¯ It is supposedthat each agent has a mentalstate neededto
create, modify,evaluate, accept or refuse proposals. The
commitment
on a retained proposal can update its mental
state. Wedenote with EmA~the mental state of the agent
Ai.
¯ Wedefine for each agent Ai a confidencecoefficient denoted with CoefA,. Thelatter associates to each agent a
value describing the degreeof confidencegranted to its
proposals. This value is obtained by a very rich mental
state anda veryvast expertise.
¯ A negotiating agent mustbe able, using its mentalstate,
to evaluatethe receivedproposals,and to submitits opinion (acceptance or refusal). For simplicity reasons,
only consider in this study the case of acceptance, since
the case of refusal generally reinitializes the processof
negotiation.
- Weexpress an acceptanceof a realization plan with a
predicate whichtakes as parameters a proposal p and
the mental state of an agent A~. Wedenote this predicate withAccept(EmA, , p ).
- Similarly, an agent must knowif another agent is able
to achieve a particular local goal. Weexpressthe fact
that an agent Ai accepts that a local goal b is carried out by another agent Ak, with a predicate denoted
Accept(EmA,,
b, Ak). In this case, we say that the agent
A~has confidence,accordingto its mentalstate, in the
agent Akto reach the goal b. It is worthnoting that an
agent alwaysaccepts its properproposal. That is to say
an agent mustbe alwaysconvincedof its ownproposal.
Realization Plan The process of negotiation starts with
the definition of a global plan related to a global goal. This
definition is the result of the negotiation of proposalsfor
global realization plan whichis suggestedby the different
agents.
(a) Proposalfor a Global Plan A proposal for global plan
is a decomposition
of a global goal in a nonemptyset of local goals. At this stage, it shouldbe notedthat a global plan
does not makeany association betweenagents and suggested
local goals. A proposalof a global goal is a subset of B£:
{bh b2..... bt} whereb~ E B£and l > 1 (1 _< i <_ l)
Duringthe process of negotiation, an agent Ascan propose
a global achievementplan for a global goal Bg~.Theset of
the proposals relating to Bgj whichcan be submittedby the
agent Ai is denotedwith:
PG(AI, Bgj) where(l_<i_<n)
and(l_<j<m)
Theset of the proposalsfor global achievementplans for the
global goal Bgj is defined as follows:
Let Bgj be a global goal, Pg an accepted global plan belonging to PGEng(Bgj),and Ai an agent. A proposal for
responsibility of local goal madeby the agent Ai relative
to P9is, in the fact, a subset of P9. Theset of these proposals is denoted with PL(AI, Pg). The set of the proposals for responsibility of the local goals of all the agentsis
the union of submitted proposals. This set is denoted by
PL(Pg). Hence:
PL(Pg) = 0 PL(AI,
i=1
It shouldbe notedthat each local goal, belongingto the plan
of resolution, mustbe part of at least oneproposalfor a local
plan.
(b) Local Goal Commitment
A local goal will be subject
of the negotiation whenit is proposedto be of the responsibility of at least twoagents. Formally:
Let b a local goal in PL(Pg).Thelocal goal b is considered
as subject of negotiationif andonly if:
3A C_ Ag. IAI _> 2 and b ¯ N PL(Ai, Pg)
A~cA
PG(Bgj) doj ~.j PG(A~,Bgj)
i=1
(b) Global Plan Commitment
A proposal for a global
plan will be subject of commitment
if it is accepted by all
agents of the society. This proposal belongsto the set defined by:
PGEn9d’d {Pg E PG(Bgj)lAcceptTot(Ag,
P9)}
(c) Global Plan AcceptanceThis can be reached according to two cases:
- all the agents accept the sameproposal;
- the agentsare in conflict (no proposalcan satisfy the first
case). In this case, the agent whichhas the highest confidencecoefficient will imposeits proposal.
Let Ai be an agent of the society, Bgj a global goal and Pgij
a proposal belongingto the set PG(AI,Bgj).
AcceptTot(Ag, P g~j ) iff
(VAk E Ag\{AI} Accept(EmAk,Pgi~)) or
(VAk E Ag\{Ai} Coef a~ > Coef k)
Local GoalDistributionThefirst step of the negotiation
considersonly the decomposition
of a global goal in a set of
local goals. Thenext step distributes the retained achievementplan on the agents of the society. Indeed,it affects to
each agentthe set of local goals whichit has to be achieved.
(a) Local Goal Proposal For the achievementof a global
goal (after definition of the global plan) the agents diffuse
their proposals for responsibility of local goals (whodoes
what), Eachproposalis a subset of the selected global plan.
122
Theset A is regardedas the set of agents that proposedto
deal with the local goal b as part of the global plan Pg. We
denote with Aneg(b, Pg) the set of all agents whoproposed
the goal b as part of Pg:
Aneg(b, Pg) %f {As ¯ Aglb ¯ PL(AI, P9)}
(c) Local Goal Acceptance The conflict between agents
mustbe solved by the agents of the society whichselect the
appropriateagent for carrying out a local goal, accordingto
their mental states (knowledgeon competencesof the various agents) or accordingto the coefficients of confidence.
Total acceptanceof a local goal can be reachedeither:
- dependingon the mental state, ke. the agent which is
readyto achievethe goal.
- or accordingto the confidencecoefficient assignedto each
agent.
AcceptTot(Ag, A~, b, Pg) iff
As ¯ Aneg(b, Pg) and
((YAk ¯ Ag\(Aneg(b, Pg)) Accept(EmA~,or
(VAt ¯ (Aneg(b, Pg)\{Ai}) CoefA, > CoefA,))
After negotiation,weassign to eachagent a set of local goals
called Role, defined as follows:
Role(Ai, Pg) %f {b Pg
l AcceptTot(Ag, Ai, b, Pg)
It is obviousthat the roles of the agents mustbe pairwise
disjunct, in order to ensure an optimalcooperation.
ResourcesDistribution In the problemsolving process,
agents generally access not only to local resources, but also
to shared resources. Theaccess to shared resources can involve simultaneous accesses, to the sameresource, which
can generate conflicts. In order to cure these anomalies,it
is necessarythat each agent reserves the neededresources
duringa set of timeintervals.
(a) NotationsFor the formal description of the process of
negotiation for allocating shared resources wesupposethe
existenceof the followingsets:
- 2 denotesthe set of all time intervals;
- 7~ denotesthe set of sharedresources;
Wedenote with Uses(Ai, b,r, I) the predicate whichindicates that the agent Ai, uses the resource r during the time
interval [ whileresolvingthe local goal b.
Let Ai be an agent, Pg a global plan. Wedefine the set of
the intervals, allocated by an agent Ai within the framework
of the global plan Pg, as:
IntR(Ai,P9)d~__r{(I,r) E 27 x I
3b C Role(Ai, Pg).Uses(A~,b, I)}
(b) Interval ProposalWedenote with PI(Ai, P9) the set
of proposals for interval allocations of resourcesneededby
the agent Ai to realize local goals as part of the resolution
plan Pg. Anagent submits a proposal in term of resources
allocation intervals with respect to global plan. Anagent
should not proposeintervals whichoverlap intervals allocated for global plan not yet completed:
PI(AI, Pg)
def
{(I,r) IntR(Ai, Pg )]
YAkE Ag, I’ E 2-.
Reserv(Ak, I’, r) ~ I n I’ = ~}
(c) Interval Commitment
A proposal for a resource allocation is subject of negotiationif the sameresourceis proposedby two different agents for time intervals whichoverlap. Wedenote the set of resource allocations whichare
subject of negotiation with Neglnt(Ag,Pg). It is definedas:
(I, r) E: Neglnt(Ag,Pg) iff
3Ai, Aj E Ag, I’ E 2-.i ¢ j and (I, r) E PI(AI, Pg) and
(I’, r) E PI(Aj, Pg) and I n I’ = 0
A Commitment
on an interval of resource allocation is made
witha real reservationof the resourceduringthe interval indicatedafter a total agreementof the proposalby all agents.
Reserv(Ai, I, r) iff AcceptTot(Ag, Ai, I, r)
(d) Allocation AcceptanceA total agreement of a proposal for a resource allocation can be reachedeither by a
correspondencebetweenthe mental state of each agent and
the proposal, or by using the confidencecoefficient if none
of the proposalscan satisfy the first case.
AcceptTot(Ag, Ai, r, I) iff
(YAke Ag\(Ai} Accept(Ai, r, I, EmA~))
(YAlE EngIR(r, I) Coef , >Coef A , )
or
where
EnglR(r,I) de=~ {A E AgISPg E PO.(I,r) E PI(A, Pg)}
123
(e) Local Plan For every agent, the process of negotiation
enables to specify a local plan definedin term of roles and
resourceallocations:
Plan(Ai, Pg) d~d (Role(Ai, Pg), Res(Ai,
where
Res(gi, Pg) %f {(i, r)i3 b C Role(Ai, Pg).
Uses(A~,b, I, r) and Reserv(Ai,I, r)}
Wedenotewith Plansthe set of all the possible plans.
Formal Model for Negotiating Agent
MentalState The set of knowledgeor facts of an agent Ai
is denotedby FactsA,. Toeach fact ¢ the agent A~assigns,
by applying a function CCA,,a coefficient of certainty denoted CCA,(¢). This is becausean agent is not alwayssure
of the truth of any given fact. Thevalue CCA,(¢) is always
between0 and 1. Accordingto this value wedistinguish two
typesof facts:
¯ Knowledge
are facts whosecoefficient of certainty equals
1.
](~A, d¢_f {~bl~b E FaCtSA,and CCA,(~3 ) : 1}
A knowledgeis a fact of whichthe agent is sure of its
truth.
¯ Beliefs are facts whosecoefficient of certainty is strictly
lower than 1.
BeIA, dcf {¢1¢ E FactsA, and CCA,(¢) < 1}
A belief is a fact of whichthe agentis not sure of its truth.
Consequently,it cannot be consideredas knowledge.
The mental state of an agent is madeup of knowledgeand
beliefs. Wedenotewith EmA~
the current mentalstate of the
agent Ai, definedas:
EmA,da ~’Ai U 13elA~
Wedenotewith Smthe set of mentalstates of the all agents.
Negotiating AgentProperties In order to be able to conclude a process of negotiation, an agent has to be equipped
witha suitable set of capabilities. Wepaya particular attention to the capability of communication.
Besides, an agent
must also be able, using its mental state, to generate and
evaluate proposals. Finally, an agent has to be autonomous
in order to makedecisions concerningthe updating of its
ownworking plan. Wedenote with Cap&the set of functionalities that an agent Ai can achieve.A capability is represented, accordingto its nature, by a function, a relation
or an elementaryprimitive (operation). Theessential capabilities neededfor the negotiation are presentedformallyas
follows:
¯ Communication
is the capability of exchanginginformation of various types: data, facts or proposals for global
plans, local plans or resourceallocations. This capability
is ensured by two primitives, namelySend and Receive:
- The primitive Send enables an agent to submit a message of any type to anotheragent. Thesubmittingagent
must specify the nameof the receiver agent, the informationtype and the messageto be sent.
- Theprimitive Receive allows the reception of messages
already sent by another agent.
Anagent Ai is said to be Communicating
if it has among
its capabilities the primitives SendandReceive.
¯ Proposal is the capability to generate proposals or
counter-proposals,using the mentalstate andthe already
madeproposals. Wedenoteswith 79 the set of all the proposals (PGU PLU PI) and 2;o the of all subsets of 79.
Anagent A~is knownas Proposingif has the capabilities Propose, CounterPropose,and Evaluate, defined as
follows:
dcf
Proposing(Ai)
3Propose,
CounterPropose,Evaluate E CaPA
~
where
Propose:
CounterPropose:
Evaluate:
References
gm x (t3G U PG u PL) ~
(e~, Bg/Pg/Pl) ~-~ Pg/Pl/Pi
$m x (Bg UPG u PL) x 2 9 ~ 79
(el, Bg/Pg/Pl, Ep) ~-* Pg/Pl/Pi
Cm × 79 ~ (Accept, Reject}
Proposedefines, using the mental state and the global
goal, global plan, or local plan, respectively, a proposal
for a global plan, a local plan or a resourceallocation.
¯ Autonomy
is the capability to generate and modifyits
ownworkingplan. At the end of the process of negotiation, an agent shoulddefine the tasks whichit mustcarry
out in order to achievethe goals specified in its role. Accordingto resource allocations over the time axis, it defines the sequenceof tasks to be carried out. Thesetasks
constitute the agendawhichis described by a sequenceof
pairs (task, time). Anagent is said to be Autonomous
if
it is able to create andmodifyits agendaaccordingto its
mentalstate andto its plan. Formally:
Agendaac=r{[(taskl,tl) .... , (task,~,t,~)]l
task~ E Tasks and t~ E Time}
def
Autonomous( Ai )
3CreateAgenda,UpdateAgendaC CaPA,
where
CreateAgenda:
Plan ×$m ~ Agenda
(p, e) ~
UpdateAgenda:
This study constitutes a part of a global approachaiming
at defining a platformfor designingand implementing
multiagent systems. At the current state of this work, a formal
validationof the modelsis essential at the semanticlevel as
well as at the behavioralone. Thusthe validated modelscan
be used in two different ways:
- as basis for a detailed analysis for the behaviorof a set of
negotiating agents.
- as a formalismfor specifying a negotiating agent system.
Acknowledgment:The authors are gratefully thankful
for MoniaLoulouand AmiraRgaiegfor their valuable contributions concerningthe specification and the implementation of the negotiating agent system.
Plan ×$m× Agenda ----* Agenda
(p, e, a) H
Conclusion
This article is centered aroundthe study of the negotiation
as a techniqueneededto supportthe cooperativeactivity in a
MAS.
Thus, wehave initially presented the conceptsrelated
to the negotiation modelsuch as proposals,their evaluations
as well as the generatedcommitments.
In the secondstep, a
modelfor negotiating agent is given. This modeldescribes
the agent’s mentalstate and the properties neededto support
negotiation. It shouldbe noted that a systemof negotiating
agent, based on the suggestedmodel,has been implemented.
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