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Computer-based systems are being used to tackle increasingly complex problems in ever more demanding domains. The size and amount of knowledge needed by such systems means they are becoming unwieldy and difficult to engineer into reliable, consistent products. One paradigm for overcoming this barrier is to decompose the problem into smaller more manageable components which can communicate and cooperate at the level of sharing processing responsibilities and information. Until recently, research in multi-agent systems has been based on ad hoc models of action and interaction; however, the notion of intentions is beginning to emerge as a prime candidate upon which a sound theory could be based. This research develops a new model of joint intentions as a means of describing the activities of groups of agents working collaboratively. The model stresses the role of intentions in controlling agents� current and future actions; defining preconditions which must be satisfied before joint problem solving can commence and prescribing how individual agents should behave once it has been established. Such a model becomes especially important in dynamic environments in which agents may possess neither complete nor correct beliefs about their world or other agents, have changeable goals and fallible actions and be subject to interruption from external events. The theory has been implemented in a general purpose cooperation framework, called GRATE*, and applied to the real-world problem of electricity transportation management. In this application, individual problem solvers have to take decisions using partial, imprecise information and respond to an ever changing external world. This fertile environment enabled the quantitative benefits of the theory to be assessed and comparisons with other models of collaborative problem solving to be undertaken. These experiments highlighted the high degree of coherence attained by GRATE* problem solving groups, even in the most dynamic and unpredictable application contexts.

This research extends a tradition of distributed theories of mind into the implementation of a distributed problem solver. In this problem solver a number of ideas from Minsky's Society of Mind are implemented and are found to provide powerful abstractions for the programming of distributed systems. These abstractions are the cauldron, a mechanism for instantiating reasoning contexts, the frame, a way of modularly describing those contexts and the goal-node, a mechanism for bringing a particular context to bear on a specific task. The implementation of both these abstractions and the distributed problem solver in which they run is described, accompanied by examples of their application to various domains.