Delete-Free Reachability Analysis for Temporal and Hierarchical Planning

Reachability analysis is a crucial part of the heuristic computation for many state of the art classical and temporal planners. In this paper, we study the difficulty that arises in assessing the reachability of actions in planning problems containing sets of interdependent actions, notably including problems with required concur-rency as well as hierarchical planning problems. We show the limitation of state-of-the-art techniques and propose a new method suitable for both temporal and hierarchical planning problems. Our proposal is evaluated on FAPE, a constraint-based temporal planner.