A Minimal Dynamical MAS Organization Model

Introduction

This chapter focuses on the presentation of the Population-Organization (PopOrg) model, a formal model for the functional and structural dynamics of open multiagent systems (MAS). The PopOrg model was introduced in (Demazeau & Costa, 1996), and revised in (Costa & Dimuro, 2008) to incorporate the notion that organizational interactions are exchange processes.

The PopOrg model is based on several principles:

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  That a MAS is best described by separately specifying its organization structure and its population structure;

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  That the core part of an organization structure is its set of organizational roles, together with the set of organizational links that relate those roles;

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  That the core part of a population structure is its set of agents, together with the set of social exchanges that relate those agents;

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  That the population structure makes the organization structure work by implementing the organizational roles and links;

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  That the organization structure constrains the set of possible behaviors and interactions that the agents may have in the system;

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  That social links between agents are exchange processes, where agents exchange services and objects among each other;

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  That organizational links are exchange processes, where roles exchange services and objects among each other;

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  That the model should be minimal, in the sense that it should have the least set of concepts enabling an adequate description of the system, but that it should be adaptable and extensible, to contemplate special features needed in particular modelling applications;

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  That the model should be extensional, in the sense that it should contemplate essentially the objective aspects of the dynamics of multiagent systems (actions performed, objects exchanged, structural changes, etc.), and that any subjective, intensional aspect (prestige, power, morality, etc.) should be added a posteriori, through specially defined intension-driven organizational rules;

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  That the forms of the intension-driven organizational rules should not constrain the definition of the model’s minimal core.

The chapter has two main goals. The first one is to extend the PopOrg model to make it contemplate the periodicity inherent in most of the organizational behaviors and interactions that happen in MAS. Such periodicity is an enabling condition for an agent’s proper assessment of the quality of its insertion in the system, which is an indispensable capability for any autonomous agent when the system is open and structurally dynamic, that is, when the agent can freely decide on entering or leaving the system, and on conserving or changing the way it is inserted in it.

The second purpose of this chapter is to illustrate the way in which the model’s extensional approach allows for the description of how intensional organizational processes operate as causal elements that may impact the extensional structure of the system. In particular, the chapter illustrates how the operational notion of morality for MAS, introduced in (Costa & Dimuro, 2007), can be supported by the model as a set of intension-driven organizational rules.

The chapter is organized as follows. Next section introduces the background of the chapter. Then, we present the latest version of the PopOrg model, the one adapted to deal with organizations where organizational interactions have a periodic character. In the sequence, we illustrate how the intensional issue of morality in multiagent systems can be tackled with the help of intension-driven organizational rules. We conclude the chapter by pointing to future research directions.