Circumscriptive Theories: A Logic-Based Framework for Knowledge Representation, Preliminary Report

Book One

Volume

Proceedings of the AAAI Conference on Artificial Intelligence, 6

Default Reasoning

The use of circumscription for formalizing commonsense knowledge and reasoning requires that a circumscription policy be selected for each particular application: we should specify which predicates are circumscribed, which predicates and functions are allowed to vary, what priorities between the circumscribed predicates are established, etc. The circumscription policy is usually described either informally or using suitable metamathematical notation. In this paper we propose a simple and general formalism which permits describing circumscription policies by axioms, included in the knowledge base along with the axioms describing the objects of reasoning. This method allows us to formalize some important forms of metalevel reasoning in the circumscriptive theory itself.