The authors investigate "partial meet contraction functions", which are defined to yield the intersection of some nonempty family of maximal subsets of the theory that fail to imply the proposition being eliminated, and basic properties of these functions are established.Expand

A representation theorem is proved which says that a revision method for a knowledge system satisfies the set of rationality postulates, if and only if, there exists an ordering of epistemic entrenchment satisfying the appropriate constraints such that this ordering determines the retraction priority of the facts of the knowledge system.Expand

The purpose is to develop a theory of such input/output operations, defined semantically and characterised by derivation rules, as well as in terms of relabeling procedures and modal operators.Expand

A notion of “safe contraction” of a set of propositions is defined, it is shown that it satisfies the Gärdenfors postulates for contraction and thus can be represented as a partial meet contraction, and its properties are studied both in general and under various natural constraints.Expand

A new version of the well-known interpolation theorem is established, which is called parallel interpolation, used to prove the splitting theorem in the infinite case, and it is shown how AGM belief change operations may be modified, if desired, so as to ensure satisfaction of Parikh's relevance criterion.Expand

The purpose of this paper is to investigate the close relations between the logic of theory change (alias belief revision) on the one hand, and nonmonotonic logic on the other. The connection is most… Expand

The relations between derogation and delivery are investigated, showing that although the two processes appear and are generally assumed to be quite different from each other, nevertheless for finite inconsistent codes, the composite process of derogating and then selecting a remainder turns out to be equipowerful with delivery.Expand