Abstract
I propose a modal logic for belief revision based on three operators representing initial beliefs, information and revised beliefs. Three axioms are put forward that express three simple principles: (1) if the agent is informed of something that he considered possible initially, then he incorporates the information in his revised beliefs, (2) if the information received is not surprising then all previous beliefs are maintained (although new beliefs may be added) and (3) any new belief must be deducible from the initial beliefs and the information received. I show that these three axioms characterize the qualitative content of Bayes' rule. I also construct a logic which is sound and complete with respect to the class of frames that satisfy the qualitative Bayes rule. Some interesting theorems are derived for extensions of this logic, for example that the agent initially believes that he later will believe A if and only if he already believes A to start with. I then extend the framework to deal with iterated belief revision and the iterated version of Bayes rule.
BibTeX  Entry
@InProceedings{bonanno:DSP:2005:330,
author = {Giacomo Bonanno},
title = {A simple modal logic for belief revision},
booktitle = {Belief Change in Rational Agents: Perspectives from Artificial Intelligence, Philosophy, and Economics},
year = {2005},
editor = {James Delgrande and Jerome Lang and Hans Rott and JeanMarc Tallon},
number = {05321},
series = {Dagstuhl Seminar Proceedings},
ISSN = {18624405},
publisher = {Internationales Begegnungs und Forschungszentrum f{\"u}r Informatik (IBFI), Schloss Dagstuhl, Germany},
address = {Dagstuhl, Germany},
URL = {http://drops.dagstuhl.de/opus/volltexte/2005/330},
annote = {Keywords: Belief revision, information, Bayes' rule, iterated revision}
}
Keywords: 

Belief revision, information, Bayes' rule, iterated revision 
Seminar: 

05321  Belief Change in Rational Agents: Perspectives from Artificial Intelligence, Philosophy, and Economics 
Issue Date: 

2005 
Date of publication: 

21.11.2005 