On team knowledge and common knowledge

We report on an approach to defining knowledge in multi-agent systems that allows the knowledge of a structured group of agents (a team) to be more than just the knowledge from individual sub-teams. Teams are first class entities in our logic. A team may have a sub-team relationship with other teams. A team which has no sub-team relationships with other teams is considered to be an agent. We ascribe knowledge directly to teams. Relationships between team and sub-team knowledge are specified axiomatically. We show that the introduction of team knowledge in this setting yields a definition of common knowledge which is an interesting generalization of the well known definition of common knowledge provided by Halpern and Moses (1992). From a systems development perspective, the separation of knowledge from sub-team knowledge allows for both top-down and bottom-up specifications of team behavior in a single framework