LiU Electronic Press
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Author:
Doherty, Patrick (Linköping University, Department of Computer and Information Science) (Linköping University, The Institute of Technology)
Title:
NML3: a non-monotonic formalism with explicit defaults
Department:
Linköping University, Department of Computer and Information Science
Linköping University, The Institute of Technology
Publication type:
Doctoral thesis, monograph (Other academic)
Language:
English
Place of publ.: Linköping, Sweden Publisher: Linköpings tekniska högskola
Pages:
290
Series:
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524; 258
Year of publ.:
1991
URI:
urn:nbn:se:liu:diva-41419
Permanent link:
http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-41419
ISBN:
91-7870-816-8
Local ID:
56320
Subject category:
Computer Science
SVEP category:
Computer science
Abstract(en) :

The thesis is a study of a particular approach to defeasible reasoning based on the notion of an information state consisting of a set of partial interpretations constrained by an information ordering. The formalism proposed, called NML3, is a non-monotonic logic with explicit defaults and is characterized by the following features: (1) The use of the strong Kleene three-valued logic as a basis. (2) The addition of an explicit default operator which enables distinguishing tentative conclusions from ordinary conclusions in the object language. (3) The use of the technique of preferential entailment to generate non-monotonic behavior. The central feature of the formalism, the use of an explicit default operator with a model theoretic semantics based on the notion of a partial interpretation, distinguishes NML3 from the existing formalisms. By capitalizing on the distinction between tentative and ordinary conclusions, NML3 provides increased expressibility in comparison to many of the standard non-monotonic formalisms and greater flexibility in the representation of subtle aspects of default reasoning.

In addition to NML3, a novel extension of the tableau-based proof technique is presented where a signed formula is tagged with a set of truth values rather than a single truth value. This is useful if the tableau-based proof technique is to be generalized to apply to the class of multi-valued logics. A refutation proof procedure may then be used to check logical consequence for the base logic used in NML3 and to provide a decision procedure for the propositional case of NML3.

A survey of a number of non-standard logics used in knowledge representation is also provided. Various formalisms are analyzed in terms of persistence properties of formulas and their use of information structures.

Public defence:
1991-10-24, Seminarierummet, Hus E, Universitetet i Linköping, Linköping, 13:15 (Swedish)
Degree:
Doctor of Philosophy (PhD)
Available from:
2009-10-10
Created:
2009-10-10
Last updated:
2013-01-16
Statistics:
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