Since the World Wide Web is an open system, it is difficult to maintain the information about services on the Web in a centralized server. Therefore the service mediation system could be constructed by federation of service communities, in which each community provides and mediates limited number of services according to its own policy. The federation should preserve the policy of each community. Furthermore, (1) scalability, (2) verifiability of policy compliance, and (3) flexibility to the change of federation relation should be considered in implementing the federation. In this paper, we introduce a notion of policy of community based on access control among players and show a community model that is aimed at specifying communications between players compliant with policy. The community model provides function specification of the service mediation system. Since a meta-architecture based language is used to describe community model, communications for the cooperation of communities can be represented separately from the communications for service request and provision. As the result, our community model (1) represents communications between players in a modular way, (2) provides a basis for verification of policy compliance, and (3) encapsulates the dependencies on partner communities.