Multi-Agent Systems and Social Networks

Background

Agents and multi-agent systems are one of the most interesting areas in software research and they have been importantly contributing to the development of the theory and the practice of complex distributed systems (Jennings et al., 1995; Muller, 1998; Bordini et al., 2005).

Although there is no single definition of an agent – see, for example, (Genesereth & Ketchpel, 1994; Wooldridge & Jennings, 1995; Russel & Norvig, 2003) – all definitions agree that an agent is essentially a special software component that: i) has autonomy; ii) provides an interoperable interface to an arbitrary system and/or iii) behaves like a human agent, working for some clients in pursuit of its own agenda. In particular, an agent i) is autonomous, because it operates without the direct intervention of humans or others and has control over its actions and internal state; ii) is reactive, because it perceives its environment, and responds in a timely fashion to changes that occur in the environment; iii) is pro-active, because it does not simply act in response to its environment and it is able to exhibit goal-directed behaviour by taking the initiative. Moreover, if necessary, an agent can be i) mobile, showing the ability to travel between different nodes in a computer network; ii) truthful, providing the certainty that it will not deliberately communicate false information; iii) benevolent, always trying to perform what is required; iv) rational, always acting in order to achieve its goals, and never to prevent its goals being achieved, and v) it can learn, adapting itself to fit its environment and to the desires of its users.

Even if a complex system can be based on a solitary agent working within its environment–that may or may not comprise users – usually agent-based systems are realized in terms of multiple, interacting agents, i.e., agent-based systems are normally multi-agent systems. Multi-agent systems are generally considered an appropriate means for modelling complex, distributed systems, even if such a multiplicity naturally introduces the possibility of having different agents with potentially conflicting goals. Agents may decide to cooperate for mutual benefit, or they may compete to serve their own interests. Agents take advantage of their social ability to exhibit flexible coordination behaviours that make them able to both cooperate in the achievement of shared goals or to compete on the acquisition of resources and tasks. Agents have the ability of coordinating their behaviours into coherent global actions.