Pseudo Extension in Default Reasoning and Belief Revision by Model Inference

Lecture Notes in Artificial Intelligence 383,27-37, 1989This paper is concerlled with extension and belief revision in Reiter\u27s default reasoning, First we introduce a new notion of pseudo extension which is successively constructed from a given default theory. We show that the set of pseudo extensions contains the set of extensions, so that we can get some reasollable candidates of extension in a constructive way. This should be a first step towards computerization of the default reasoning. We also discuss the belief revision problem from the viewpoint of Shapiro\u27s inductive inference of models