Cost-Optimal Planning with Landmarks

Planning landmarks are facts that must be true at some point in every solution plan. Previous work has very successfully exploited planning landmarks in satisficing (non-optimal) planning. We propose a methodology for deriving admissible heuristic estimates for cost-optimal planning from a set of planning landmarks. The resulting heuristics fall into a novel class of multi-path dependent heuristics, and we present a simple best-first search procedure exploiting such heuristics. Our empirical evaluation shows that this framework favorably competes with the state-of-the-art of cost-optimal heuristic search.