A Two-Stage Approach to First Order Default Reasoning

Article type: Research Article

Authors: Schlechta, Karl

Affiliations: Laboratoire d'Informatique de Marseille, URA CNRS 1787, CMI, Technopôle de Château-Gombert, F-13453 Marseille Cedex 13, France. [email protected]

Abstract: Our subject is the representation and analysis of simple first-order default statements of ordinary language, such as “normally, birds fly”. There are, among other approaches, two kinds of analysis, both semantic in style. One interprets “normally, birds fly” along the lines of “for every item x in the domain of discourse, the most normal models of “x is a bird” are models of “x flies””. This is the preferential models approach, first outlined by Bossu/Siegel and Shoham, and studied by Kraus, Lehmann, Magidor and others. The other interprets “normally, birds fly” along the lines of “there is an important subset of the birds, all of whose elements fly”. This is the generalized quantifier approach, formulated and developed by the author. The purpose of the present paper is to show how the two approaches may usefully be combined into a single two-stage approach, and how such a combination provides an elegant account of certain problematic examples.

Keywords: Nonmonotonic Logic, Defaults, Preferential Models, Generalized Quantifiers

DOI: 10.3233/FI-1996-283412

Journal: Fundamenta Informaticae, vol. 28, no. 3-4, pp. 377-402, 1996