On the Use of Landmarks in LPG

Domain-Independent planning is notoriously a very hard search problem. In the literature, several techniques for search control have been proposed in the context of various planning formalisms. In particular, Landmark techniques have been widely used in the planning community in order to guide the search process or to define heuristic functions. A Landmark can be defined as a logical expression, consisting of facts or actions, that certainly becomes true in any solution plan for that problem. In this work, we propose the use of Landmarks for the LPG planner, considering different design choices and analysing empirically its impact on the performance of the planner. Preliminary results show that these techniques can effectively improve the performance of LPG, obtaining results comparable with the state-of-the-art planner LAMA.