formed by all agents in the system, possibly arising from their communication and interaction via observation. According to the authors, a set of actions committed by different agents is stable **if, assuming that an "oracle" could feed each of the**
agents with all the actions in the set performed by the other agents, each agent would do exactly what is in the set. We believe that such a machinery is similar to our fixpoint-based approach since we guess candidate social interpretations and select those which are compatible with the SCs of the SOLP collection.

In our work we focused on the formalization of the semantics, assuming a perfect communication among the agents in such a way that each agent is able **to know the**
mental state of the others. Using a different approach from ours, in (Satoh and Yamamoto 2002),
in order to face the possible incompleteness of information due to communication failures or delays in a multi-agent system, a default hypothesis is used as a tentative answer and the computation continues until a reply is received which **contradicts** with the default.

Another interesting work is the MINERVA agent architecture (Leite et al. 2002),
based on dynamic logic programming (Alferes et al. 2000). MINERVA is **a modular** architecture, where every agent is composed of specialized sub-agents that execute special tasks, e.g., reactivity, planning, scheduling, belief revision, **action execution.** A common internal knowledge base, represented as one or more Multi-dimensional Dynamic Logic Programs (MDLP) (Alferes et al. 2002), is concurrently manipulated by its specialized sub-agents. The MDLPs may encode object-level knowledge, or knowledge about goals, plans, intentions, etc.

The DALI project (Costantini and Tocchio 2002) is a complete multi-agent platform entirely written in Prolog. A DALI program results in an agent which is capable of reactive and proactive behaviour, triggered by several kinds of events. The semantics of a DALI program is defined in terms of another program, where reactive and proactive rules are reinterpreted as standard Horn **Clause rules.**
Laima (De Vos et al. 2005) agents are represented as Ordered Choice Logic Programs (OCLP) (De Vos 2003) for modelling their knowledge and reasoning capabilities. Communication between the agents is regulated by uni-directional channels transporting information based on their answer sets.

IMPACT (Subrahmanian et al. 2000) is an agent platform where programs may be used to specify what an agent is either obliged to do, may do, or cannot do on the basis of deontic operators of permission, obligation and prohibition. IMPACT is grounded on a solid semantic framework based on the concept of feasible status set, which describes a set of actions dictated by an agent program **that is consistent** with the obligations and restrictions on the agent itself. Agent programs define integrity constraints, which must be satisfied in order to provide a feasible status set. The adoption of a logic programming based formalism, and the use of integrity constraints to define a feasible status set, guarantee agents to **behave in a way that** some desired properties hold.

Societies Of ComputeeS (SOCS) (Alberti et al. 2004) is a project that was funded by European Union. The idea is to provide a computational logic model **for the**
description, analysis and verification of global and open societies of **heterogeneous**
computees. The computee model is proposed as a full-fledged agent model, based