G-STRIPS – A Generalized STRIPS System for Handling State Change over Dynamic Domains

Abstract

State change is an essential issue in robotic dynamics modeling. In this paper, we investigate this issue over dynamic domains in the sense that an object in the domain may be created or destroyed by executing some plan of the system. It is observed that current logic based dynamic systems, e.g. the STRIPS-like systems, are semantically problematic to deal with dynamic domains in state change. It turns out that representing nonexisting objects in a logic system becomes a key point to handle this problem. Based on this observation, we define N-structures for an arbitrary first order language where syntactic terms are allowed to denote nonexisting objects with respect to the domain of quantification. Using N-structures to model dynamic domains, we then generalize classical STRIPS to G-STRIPS which can represent and reason about state change involving creation or destruction of objects. We also specify a provablely correct semantics for a class of G-STRIPS systems based on N-structures.