Structural Symmetries of the Lifted Representation of Classical Planning Tasks

Abstract

We transfer the notion of structural symmetries to lifted planning task representations, based on a generalizing concept of abstract structures we use to model planning tasks. We show that symmetries are preserved by common grounding methods and shed some light on the relation to previous symmetry concepts. An analysis of common planning benchmarks reveals that symmetries occur in the lifted representation of many domains. Our concept prepares the ground for exploiting symmetries beyond their current scope, such as for faster grounding and mutex generation, as well as for state space transformations and state space reductions.