Multi-agency Is Coordination and (Limited) Communication

Systems within the agent-oriented paradigm range from ones where a single agent is coupled with an environment to ones inhabited by a large number of autonomous entities. In this paper, we look at what distinguishes single-agent systems from multi-agent systems. We claim that multi-agency implies limited coordination, in terms of action and/or information. If a team is characterized by full coordination both on the level of action choice and the available information, then we may as well see the team as a single agent in disguise. To back the claim formally, we consider a variant of Alternating-time Temporal Logic atl where each coalition operates with a single indistinguishability relation. For this variant, we propose a truth-preserving translation of formulas and models in the syntactic fragment of atl where only singleton coalitions are allowed. In consequence, we show that assuming unified view of the world on part of each coalition reduces the full language of atl to its single-agent fragment when a model is given.