KR2020Proceedings of the 17th International Conference on Principles of Knowledge Representation and ReasoningProceedings of the 17th International Conference on Principles of Knowledge Representation and Reasoning

Rhodes, Greece. September 12-18, 2020.

Edited by

ISSN: 2334-1033
ISBN: 978-0-9992411-7-2

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Published by

Copyright © 2020 International Joint Conferences on Artificial Intelligence Organization

Rational Defeasible Belief Change

  1. Giovanni Casini(ISTI-CNR, CAIR, University of Cape Town)
  2. Thomas Meyer(University of Cape Town, CAIR)
  3. Ivan Varzinczak(CRIL, Univ. Artois, CNRS, CAIR, Stellenbosch University)


  1. Belief revision and update, belief merging, information fusion-General
  2. Nonmonotonic logics, default logics, conditional logics-General


We present a formal framework for modelling belief change within a nonmonotonic reasoning system. Belief change and non-monotonic reasoning are two areas that are formally closely related, with recent attention being paid towards the analysis of belief change within a non-monotonic environment. In this paper we consider the classical AGM belief change operators, contraction and revision, applied to a defeasible setting in the style of Kraus, Lehmann, and Magidor. The investigation leads us to the consideration of the problem of iterated change, generalising the classical work of Darwiche and Pearl. We characterise a family of operators for iterated revision, followed by an analogous characterisation of operators for iterated contraction. We start considering belief change operators aimed at preserving logical consistency, and then characterise analogous operators aimed at the preservation of coherence—an important notion within the field of logic-based ontologies.