On Generalizing the AGM Postulates

Giorgos Flouris
Dimitris Plexousakis
Grigoris Antoniou

Institute of Computer Science, FO.R.T.H. 
P.O. Box 1385, GR 71110, Heraklion, Greece
{fgeo, dp, antoniou}@ics.forth.gr

Abstract
The AGM theory is the dominating paradigm in the field of belief 
change but makes some non-elementary assumptions which disallow 
its application to certain logics. In this paper, we recast the 
theory by dropping most such assumptions; we determine necessary 
and sufficient conditions for a logic to support operators which 
are compatible with our generalized version of the theory and show 
that our approach is applicable to a broader class of logics than 
the one considered by AGM. Moreover, we present a new representation 
theorem for operators satisfying the AGM postulates and investigate 
why the AGM postulates are incompatible with the foundational model. 
Finally, we propose a weakening of the recovery postulate which has 
several intuitively appealing properties.