Please use this identifier to cite or link to this item: http://hdl.handle.net/10525/974

 Title: Representing Default Logic in Modal Logic Authors: Brown, Frank Keywords: Default LogicModal LogicNonmonotonic Logic Issue Date: 2003 Publisher: Institute of Information Theories and Applications FOI ITHEA Abstract: The nonmonotonic logic called Default Logic is shown to be representable in a monotonic Modal Quantificational Logic whose modal laws are stronger than S5. Specifically, it is proven that a set of sentences of First Order Logic is a fixed-point of the fixed-point equation of Default Logic with an initial set of axioms and defaults if and only if the meaning or rather disquotation of that set of sentences is logically equivalent to a particular modal functor of the meanings of that initial set of sentences and of the sentences in those defaults. This result is important because the modal representation allows the use of powerful automatic deduction systems for Modal Logic and because unlike the original Default Logic, it is easily generalized to the case where quantified variables may be shared across the scope of the components of the defaults thus allowing such defaults to produce quantified consequences. Furthermore, this generalization properly treats such quantifiers since both the Barcan Formula and its converse hold. URI: http://hdl.handle.net/10525/974 ISSN: 1313-0463 Appears in Collections: Volume 10 Number 4

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