An argument for a hybrid HTN/operator-based approach to planning

Abstract

Work on generative planning systems has focused on two diverse approaches to plan construction. Hierarchical task network (HTN) planners build plans by successively refining high-level goals into lower-level activities. Operator-based planners employ means-end analysis to formulate plans consisting of low-level activities. While many have argued the universal dominance of a single approach, we present an alternative view: that in different situations either may be most appropriate. To support this view, we describe a number of advantages and disadvantages of these approaches in light of our experiences in developing two real-world, fielded planning systems.