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  • On the logic of theory change: contraction without recovery
    Publication . Fermé, Eduardo L.
    The postulate of Recovery, among the six postulates for theory contraction, formulated and studied by Alchourron, G ´ ardenfors and Makinson is the one that has provoked most controversy. ¨ In this article we construct withdrawal functions that do not satisfy Recovery, but try to preserve minimal change, and relate these withdrawal functions with the AGM contraction functions.
  • Selective revision
    Publication . Fermé, Eduardo L.; Hansson, Sven Ove
    We introduce a constructive model of selective belief revision in which it is possible to accept only a part of the input information. A selective revision operator ο is defined by the equality K ο α = K * f(α), where * is an AGM revision operator and f a function, typically with the property ⊢ α → f(α). Axiomatic characterizations are provided for three variants of selective revision.
  • A brief note about Rott contraction
    Publication . Fermé, Eduardo L.; Rodriguez, Ricardo O.
    One of the ways to model contraction functions for belief sets is epistemic entrenchment. The first step was provided by G¨ardenfors in [5], who defined epistemic entrenchment and a contraction function in terms of it and related the latter with the AGM contraction function. Later Hans Rott in [16] presented an entrenchment based contraction function that does not satisfy recovery. In this paper we provide an axiomatic characterization of Rott Contraction.1