Best - first search for property main - tenance in reactive constraints sys - tems

Real-life dynamic problems may lead to inconsistent constraints systems for which a solution must be found even if constraints have to be relaxed. In this paper, we propose a best-first search to handle such problems. Classical backtracking search algorithms are extended in two ways: identification of good backtrack points as in Intelligent Backtracking techniques and maximum use of independant work (that would have been discarded with a mere backtrack). We first describe an operational semantics for our search method. Then we specialize it to handle constraint relaxation over finite domains. The practical use of this approach is demonstrated by theoretical complexity analysis and experiments.