On the separation of propositional and numeric planning in realistic problems

Abstract. State-of-the-art planners need to use different strategies to cope with the increasing complexity of realistic planning problems. These strategies tend to simplify the problem to make it more affordable. The separation of the planning and scheduling parts, the relaxation of the original problem, the application of heuristics, etc. are usual in modern planning. In this paper, we present an ongoing approach that divides the planning process into two consecutive stages. First, a sequential plan is generated by discarding the numeric conditions/effects of actions, thus ignoring the scheduling part of the problem. Second, this plan is parallelised while the satisfaction of numeric constraints is guaranteed, thus taking the scheduling part of the problem into account. Both stages use heuristic estimations calculated through a relaxed version of a planning graph that help reduce the search space.