Date of Award


Publication Type

Master Thesis

Degree Name



Computer Science


Computer Science.


Morrissey, Joan,




An active area of research is to find a logic which models human commonsense reasoning. Several non-monotonic logics have been proposed. However, each has deficiencies associated with it. Default Logic is one such non-monotonic formalism. We examine some of the problems with Default Logic as pointed out by (Nut83, Nut87, Isr80, Pea90) and present an approach which addresses some of these deficiencies. In our approach, we attach a certainty factor to each statement in the knowledge base and use this information to give the user the most certain answer to a query. This gives us a certainty factor default logic (CFDL). We present the syntax semantics and proof theory for this logic. A resolution algorithm has been developed and implemented. This implementation shows that the proposed logic works with some benchmark examples (Lif89) for non-monotonic reasoning. It can also be used as a testbed for different calculi of uncertainty. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1994 .P373. Source: Masters Abstracts International, Volume: 34-02, page: 0793. Adviser: Joan Morrissey. Thesis (M.Sc.)--University of Windsor (Canada), 1994.