The Distributed Constraint Satisfaction Problem :

In this paper, we develop a formalism called a distributed constraint satisfaction problem (distributed CSP) and algorithms for solving distributed CSPs. A distributed CSP is a constraint satisfaction problem in which variables and constraints are distributed among multiple agents. Various application problems in Distributed Arti cial Intelligence can be formalized as distributed CSPs. We present our newly developed technique called asynchronous backtracking that allows agents to act asynchronously and concurrently without any global control, while guaranteeing the completeness of the algorithm. Furthermore, we describe how the asynchronous backtracking algorithm can be modi ed into a more e cient algorithm called asynchronous weak-commitment search, which can revise a bad decision without exhaustive search by changing the priority order of agents dynamically. The experimental results on various example problems show that the asynchronous weak-commitment search algorithm is by far more e cient than the asynchronous backtracking algorithm and can solve fairly large-scale problems. Makoto Yokoo is with NTT Communication Science Laboratories, Kyoto, Japan. E-mail: [email protected] . Edmund H. Durfee is with Dept. of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, U.S.A. E-mail: [email protected] . Toru Ishida is with Dept. of Information Science, Kyoto University, Kyoto, Japan. E-mail: [email protected] . Kazuhiro Kuwabara is with Nippon Telegraph and Telephone Corporation, Tokyo, Japan. E-mail: [email protected] . This paper is the extended version of the authors' previous conference papers [21],[22].