Similarity preservation in default logic

Rachel Ben-Eliyahu-Zohary, Nissim Francez, Michael Kaminski

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


The paper identifies a problem in default reasoning in Reiter's Default Logic and related systems: elements which are similar given the axioms only, become distinguishable in extensions. We explain why, sometimes, this is considered undesirable. Two approaches are presented for guaranteeing similarity preservation: One approach formalizes a way of uniformly applying the defaults to all similar elements by introducing generic extensions, which depend only on similarity types of objects. According to the second approach, for a restricted class of default theories, a default theory is viewed as a "shorthand notation" to what is "really meant" by its formulation. In this approach we propose a rewriting of defaults in a form that guarantees similarity preservation of the modified theory. It turns out that the above two approaches yield the same result.

Original languageEnglish
Pages (from-to)137-160
Number of pages24
JournalAnnals of Mathematics and Artificial Intelligence
Issue number1-2
StatePublished - 1 Jan 1999

ASJC Scopus subject areas

  • Artificial Intelligence
  • Applied Mathematics


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