Publication Details

This article was originally published as Ghose, AK, Hadjinian, PO, Sattar, A, You, J and Goebel, R, Iterated belief change, Computational Intelligence, 2004, 20(1), 37-55. The definitive version is available at www.blackwell-synergy.com. Copyright 2004 Blackwell Publishing.


Most existing formalizations treat belief change as a single step process, and ignore several problems that become important when a theory, or belief state, is revised over several steps. This paper identifies these problems, and argues for the need to retain all of the multiple possible outcomes of a belief change step, and for a framework in which the effects of a belief change step persist as long as is consistently possible. To demonstrate that such a formalization is indeed possible, we develop a framework which uses the language of PJ-default logic to represent a belief state, and which enables the effects of a belief change step to presist by propagating belief constraints. Belief change in this framework maps one belief state to another, where each belief state is a collection of theories given by the set of extensions of the PJ-default theory representing that belief state. Belief constraints do not need to be separately recorded; they are encoded as clearly identifiable components of a PJ-default theory. The framework meets the requirements for iterated belief change that we identify and satisfies most of the AGM postulates as well.