Revisiting Regression in Planning

Heuristic search with reachability-based heuristics is arguably the most successful paradigm in Automated Planning to date. In its earlier stages of development, heuristic search was proposed as both forward and backward search. Due to the disadvantages of backward search, in the last decade researchers focused mainly on forward search, and backward search was abandoned for the most part as a valid alternative. In the last years, important advancements regarding both the theoretical understanding and the performance of heuristic search have been achieved, applied mainly to forward search planners. In this work we revisit regression in planning with reachabilitybased heuristics, trying to extrapolate to backward search current lines of research that were not as well understood as they are now.