Belief Revision and Ordered Theory Presentations.
Mark Dermot Ryan · 1996
The standard theory of belief revision|known as the AGM theory after its authors, C. Al-chourron, P. Gardenfors and D. Makinson [3]|suers from at least two disadvantages. One is that it represents belief states as innite objects, namely deductively closed sets of sentences. Another is that existing belief revision models make too strong assumptions about what in-formation is available to guide revisions. A consequence of this is that repeated revisions are impossible. In this paper, we show how to use ordered theory presentations to represent belief states 1 Ordered theory presentations are theory presentations equipped with a partial order. In this paper we are only concerned with a special case, in which the sets are nite and the order is total, or linear. We dene a revision operator, which is shown to satisfy some, but not all, of the AGM postulates. No information other than that encoded in the OTP is needed to eect the revision; this makes repeated revision easy. 1