Title:	Taking Levi Identity Seriously: a plea for iterated belief contraction
Date:	April 6, 2006 (Thursday)
Time:	2:30 p.m. - 3:30 p.m.
Venue:	Room 121, 1/F, Ho Sin-hang Engineering Building, The Chinese University of Hong Kong, Shatin, N.T.
Speaker:	Dr. Abhaya Nayak Department of Computing Macquarie University Australia

ABSTRACT:

Intelligent behaviour assumes that when an agent receives a new piece of information (an observation, a piece of evidence), it can accommodate it into its current stock of beliefs in a rational fashion. Under the simplifying assumption that the observation has been checked out and should be "accepted", a problem arises if it conflicts with the current stock of beliefs. Naturally, some of the current beliefs have to jettisoned in order to make room for the new observation. Reason dictates that such loss of information should be minimised. But typically there are far too many ways of doing it. The problem of belief contraction involdes investigating the rational ways of discarding some information from one's belief corpus. The classical account of belief change provides a framework for "one-shot" belief contraction (and belief revision); but it leaves open the issue of how an agent can perform a sequence of belief contractions in a rational manner. This talk discusses why it is important to have an account of iterated belief contraction, and suggests one interesting way of doing it.

Most work on iterated belief change has focused on iterated belief revision, namely how to compute (K*x)*y. Historically however, belief revision can be defined in terms of belief expansion and belief contraction, where expansion and contraction are viewed as primary operators. Accordingly, our attention to iterated belief change should be focused on constructions like (K+x)+y, (K-x)+y, (K+x)-y and (K-x)-y. The first two of these are relatively straightforward, but the last two are more problematic. Here we consider these latter, and formulate iterated belief change by employing the Levi identity and the Harper Identity as the guiding principles.

BIOGRAPHY:

Abhaya Nayak is a faculty member in the Department of Computing at Macquarie University (Australia). He did his doctoral research at the University of Rochester (USA) under the supervision of Professor Henry Kyburg Jr. His research interests include Belief Revision, Nonmonotonic Reasoning, Reasoning about Action, and Intelligent Information Assimilation. He is particularly interested in the application of Social Choice Theory in the context of information management.

Enquiries: Miss Temmy So at tel 2609 8444

For more information, please refer to http://www.cse.cuhk.edu.hk/seminar