Partial meet pseudo-contractions

Abstract

In the AGM paradigm for belief revision, epistemic states are represented by logically closed sets of sentences, the so-called belief sets. An alternative approach uses belief bases, arbitrary sets of sentences. Both approaches have their problems when it comes to contraction operations. Belief bases are more expressive, but, at the same time, they present a serious syntax dependence.Between those two extremes lie a whole gamut of operations called pseudo-contractions, some of which may be interesting alternatives to the classical ones, providing a good balance between syntax dependence and expressivity.In this paper we explore some very natural and general constructions for pseudo-contractions, showing some of their properties and giving their axiomatic characterizations. We also illustrate possible practical scenarios where they can be employed.