Formalising the contract net as a goal-directed system

Abstract

In response to the problems that have arisen regarding the terminology and concepts of agent-oriented systems, previous work has described a formal framework for understanding agency and autonomy. In this paper we outline the framework and refine it by adding further levels of detail to develop a formal model of the Contract Net Protocol. The model serves to make precise both the operations of nodes in the contract net, and the state of the net at various points during the protocol. In particular, the nature of the dependencies between the nodes in the net is explicated. Finally, we generalise the relationships that can be found in the contract net which are brought out by the formalisation, and introduce more general concepts such as cooperation and engagement.