Explaining Explanation Closure

Recently Haas Schubert and Reiter have developed an al ternative approach to the frame problem which is based on the idea of using explanation closure axioms The claim is that there is a mono tonic solution for characterizing nonchange in serial worlds with fully speci ed actions where one can have both a succinct representation of frame axioms and an e ective proof theory for the characterization In the paper we propose a circumscriptive version of explanation closure PMON that has an e ective proof theory and works for both context dependent and nondeterministic actions The approach retains represen tational succinctness and a large degree of elaboration tolerance since the process of generating closure axioms is fully automated and is of no concern to the knowledge engineer In addition we argue that the monotonic nonmonotonic dichotomy proposed by others is not as sharp as previously claimed and is not fully justi ed Accepted for publication at the th Int l Symposium on Methodologies for Intelligent Systems Zakopane Poland June