A Knowledge-Based Framework for Belief Change. Part II: Revision and Update
N. Friedman and J. Y. Halpern
In J. Doyle, E.
Sandwell, and P. Torasso, eds. Principles of Knowledge
Representation and Reasoning: Proc. Fourth International Conference
(KR'94). Morgan Kaufman, San Francisco, CA. 1994. 190-201.
The study of belief change has been an active area in
philosophy and AI. In recent years two
special cases of belief change, belief revision and
belief update, have
been studied in detail. In a companion paper (Friedman&Halpern,1994) we
introduced a new
framework to model belief change. This framework combines
temporal and epistemic modalities with a notion of plausibility,
allowing us to examine the changes of beliefs over
In this paper we
show how belief revision and belief update can be captured in our
This allows us to compare the assumptions made by each method
and to better understand the principles underlying them.
allows us to understand the
source of Gardenfors'
triviality result for belief revision (Gardenfors,1986) and
suggests a way of
mitigating the problem.
It also shows that Katsuno and Mendelzon's (1991) notion
of belief update depends on several
assumptions that may limit its applicability in
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