Integrating planning and execution which treats either component as a black box may lead to disparate representations of the domain or information currently known. Consistency and bidirectional information flow are then hard to ensure. However, the separation of these concerns is still useful from an integration point of view.
In this paper, we discuss the integration of planning systems using the Planning Domain Definition Language (PDDL) with an executive based on the CLIPS rule-based production system. In particular, we describe how we achieved one common and unified domain model used by both systems and some additions we add for the execution model. We also show how the execution model enables effective execution monitoring and selective replanning.