Translating HTNs to PDDL: A small amount of domain knowledge can go a long way

We show how to translate HTN domain descrip- tions (if they satisfy certain restrictions) into PDDL so that they can be used by classical planners. We provide correctness results for our translation al- gorithm, and show that it runs in linear time and space. We also show that even small and incom- plete amounts of HTN knowledge, when translated into PDDL using our algorithm, can greatly im- prove a classical planner’s performance. In ex- periments on several thousand randomly gener- ated problems in three different planning domains, such knowledge speeded up the well-known Fast- Forward planner by several orders of magnitude, and enabled it to solve much larger problems than it could otherwise solve.