Abstract

Contracts are a powerful co-ordination mechanism in distributed systems. The contract net protocol has been applied since about 1980. The CNP distributes tasks to different problem-solving nodes. TRACONET extended CNP with a bidding and awarding decision process based on marginal cost calculations. The CIA(Cooperative Information Agent) framework introduced the notion of obligations, which was broadened by CAS (Contractual Agent Societies) to support the fluid organisation of agent societies. Finally, the TPA framework (Trading Partner Agreement) introduced by IBM, although not agent-based, uses contracts as well, it uses executable contract in particular. We will analyse these four different contract model related researches (CNP, TRACONET, CAS and TPA) to compare their capabilities, background assumptions and limitations. We propose an integrated architecture and discuss the essential requirements still to be met.