We consider the challenges that arise when plans are based on an incorrect representation of the domain in which they are executed. We describe how information about plan formation, and how the way in which each plan step is related to the domain representation, can help identify problems in the underlying ontology when plan failure is encountered. We introduce the notion of a plan deconstructor, used to extract this information from the domain representation so that is it available when plan failure occurs. Thus a more accurate ontology can be developed and more robust plans can be formed.