FLECS: Planning with a Flexible Commitment Strategy

There has been evidence that least-commitment planners can e ciently handle planning problems that involve di cult goal interactions. This evidence has led to the commonbelief that delayed-commitment is the \best" possible planning strategy. However, we recently found evidence that eager-commitment planners can handle a variety of planning problems more e ciently, in particular those with di cult operator choices. Resigned to the futility of trying to nd a universally successful planning strategy, we devised a planner that can be used to study which domains and problems are best for which planning strategies. In this article we introduce this new planning algorithm, flecs, which uses a FLExible Commitment Strategy with respect to plan-step orderings. It is able to use any strategy from delayed-commitment to eager-commitment. The combination of delayed and eager operator-ordering commitments allows flecs to take advantage of the bene ts of explicitly using a simulated execution state and reasoning about planning constraints. flecs can vary its commitment strategy across di erent problems and domains, and also during the course of a single planning problem. flecs represents a novel contribution to planning in that it explicitly provides the choice of which commitment strategy to use while planning. flecs provides a framework to investigate the mapping from planning domains and problems to e cient planning strategies.