Co-ordination is the glue that binds the activities of autonomous problem-solving agents together into a functional whole. Co-ordination mechanisms for distributed problem-solving usually rely on a central coordinator that orchestrates agent behaviour or just replicate a centralised mechanism among many agents. Social co-ordination is a decentralised mechanism, in which the mutual adaptation of the behaviour of autonomous agents emerges from the interrelation of the agents' self-interests. The few existent models of social co-ordination are based either on sociologic or on economic findings. Still, they usually refer to heterogeneous agent societies and are rarely concerned with the co-ordination of problem-solving activities. In this paper we present a formal framework that unifies the sociological and the economic approach to decentralised social co-ordination. We show how this model can be used to determine the outcome of decentralised social co-ordination within distributed pr...