# Towards a Model of MultiAgent Systems' Organization

Mahdi Hannoun, Olivier Boissier, Claudette Sayettat, Jaime Simao Sichman

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Mahdi Hannoun, Olivier Boissier, Claudette Sayettat, Jaime Simao Sichman. Towards a Model of MultiAgent Systems' Organization. CMOT'98 - International Workshop on Computational and Mathematical Organization Theory, Apr 1998, Montréal, Canada. emse-00758141

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# Towards a Model of Multi-Agent Systems'
## Organization

Mahdi Hannoun(1), Olivier Boissier(1), Claudette Sayettat(1)
and Jaime Simão Sichman(2)

(1)Departement Systèmes Industriels Coopératifs, SIMADE,
École des Mines, 158 cours Fauriel, 42023 Saint-Etienne, France
e-mail: {hannoun,boissier,sayettat}@emse.fr

(2)University of São Paulo, Computer Engineering Department,
av. Prof. Luciano Gualberto, 158, tv. 3, 05508-900, São Paulo, SP, Brazil
e-mail: jaime@pcs.usp.br

## 1 Introduction

With the growing interest in Multi-Agent Systems (MAS), the need of useful tools to design such systems is an important concern of research. As initiated in the ASIC model [1] and developed in [2], modeling a complex and decentralized system using MAS technics can be viewed through four main axes: agents, interactions, organizations and the environment in which agents interact.

In this context, we are interested in modeling the organization of a MAS. For us, the organization axe deals with the structure of the agents in the system, along different schemes (hierarchy, team, group...), in order to control their processing.

In our opinion, this structure is related to the definition of responsibilities regarding the execution of missions among agents. Considering the MAS research scenario, two main approaches can be found : a pre-defined one and an emergent one. In the pre-defined approach, this structure constrains the functioning of the agents (i.e, it is a design constraint) whereas in the emergent approach, this structure is the result of the functioning of the agents.

In this paper, we are mainly concerned with the first approach. We present an organizational model whose core notions are organisational roles and links. This model is currently used for the specification of a groupware application using a MAS approach.

## 2 Modeling the Organizational Structure

Organization is a field of interest in different domains: ethology, biology, economics, sociology... In MAS, an organization is often expressed as a set of roles and links between them. What these roles and links are depends on the authors [3, 4]. Schematically, the organization, enables to express *who* does *what*, *when* one does it and often *how* one does it.
Our model of a MAS organization [5] is decomposed into an organizational structure (OS) and an organizational entity (OE) :

* The OS is defined as a graph of organizational *roles* and organizational *links* between them;

* The OE is a set of agents of the system, structured according to an OS: agents are associated to roles and connected according to the corresponding links, i.e, it is a kind of instantiation of an OS.

## 2.1 Roles

A role is a coherent collection of *missions*. A mission is defined by a *quadruple* of four sets: *goals, plans, actions and resources*. Each set can be eventually empty. The goal set defines the goals to achieve for the defined mission. The plan set defines the plans to follow, the action set, the actions to execute, and the resource set, the resources to be used.

The combination of these four sets, allows us to define and constrain a mission with more flexibility. For example, a mission defined with only goals, allows the agent that fulfills this mission to define its own plans, using any actions and resources. In this sense, it is less constrained than an agent that has to fulfill a mission with specified plans, actions and/or resources to use.

## 2.2 Organizational Links

An organizational link is a directed arc between two roles. It can be an *authority* link, a *communication* link or an *acquaintance* link. This link is labelled by a possibly empty subset of missions of the source role and subset of missions of the target role. Through these links, agents playing the source role of the link, may respectively control, communicate or represent the agents playing the target role, in the context of the missions qualifying the link.

The roles and the set of three links, authority, communication and acquaintance, can be viewed as a superposition of three graphs respectively the control graph, the communication graph and the acquaintance graph.

The control graph represents control paths among roles in the organization. It defines the degree of control/influence that agents playing the source role may carry on agents playing the target roles.

The communication graph represents the path of allowed information transit in the organization. The aim of the graph is to better represent the organization data flow.

The acquaintance links allow the agents to have knowledge and maintain a representation of other agents. These knowledges and representations can concern the dependence relations between these agents, the skills of these agents, the degree of preference, etc., and it can help an agent to choose an interlocutor for a particular cooperation.

## 3 Conclusion

In this paper, we have presented a first step towards modeling the organization in a MAS. We have proposed a structure of agents in a system according to OS,
which is composed of roles and links. The use of this model is currently applied
on a groupware application.

This is a first attempt to validate our model that enables us to envisage
different perspectives of development. First, we have to enrich the formalization
of the roles and links especially to ensure a well defined semantics on these
concepts (deontic logic should be a good candidate). In parallel, we have started
to study the validation of these organizational structures in terms of coherence:
is such an authority link justified bebetween these roles [6] in face of existing
dependence relation [7]. Besides the definition of a MAS organization, we have
then to start to design agents that are themselves able to design and settle such
organizational structures dynamically in an emergent approach.

References

[1] Olivier Boissier.: *The control Problem in an Integrated Vision System. A Multi-Agent Approach*, PhD thesis, LIFIA Laboratory, Grenoble, France, jan-uary 1993. in french.

[2] Yves Demazeau.: From Cognitive Interactions to Collective Behaviour in Agent-Based Systems, *Proceeding of the 1st European Conference on Cognitive Science*, Saint-Malo, France, 1995.

[3] Gil Tidhar, Anand S. Rao and Elizabeth A. Sonenberg.: Guided Team Selection, *Proceeding of Second International Conference on Multi-Agent Systems ICMAS'96*, Kyoto, Japan, 1996.

[4] Norbert Glaser and Philippe Morignot.: The Reorganization of Societies of Autonomous Agents. *Proceeding of 8th European Workshop on Modelling Autonomous Agents in Multi-Agent World*, Sweden, May, 1997.

[5] Mahdi Hannoun.: *Modelling Organization in Multi-Agent System*. RR 98.02, Laboratoire SIC - École des Mines de Saint-Etienne - France, January 1998. in french.

[6] Mahdi Hannoun, Jaime Simão Sichman, Olivier Boissier and Claudette Sayettat.: Dependence relation between roles in a multi-agent system. Submitted to the Workshop on Multi-Agent Systems and Agent-Based Simulation, Mabs'98, 1998.

[7] Jaime Simão Sichman, Rosario Conte, Yves Demazeau, and Christiano Castelfranchi.: A social reasoning mechanism based on dependences networks. In Tony Cohen, editor, *Proceeding of the 11th European Conference on Artificial Intelligence*, Amsterdam, The Netherlands, August 1994.