finin@PRC.Unisys.COM (03/18/88)
AI SEMINAR UNISYS PAOLI RESEARCH CENTER A Formalization of Inheritance Hierarchies with Exceptions and Multiple Ancestors Lokendra Shastri University of Pennsylvania Many knowledge-based systems express domain knowledge in terms of a hierarchy of concepts/frames - where each concept is a collection of attribute-value (or slot-filler pairs). Such information structures are variably referred to as frame-based languages, semantic networks, inheritance hierachies, etc. One can associate two interesting classes of inference with such information structures, namely, inheritance and classification. Attempts at formalizing inheritance and classification, however, have been confounded by the presence of conflicting attribute-values among related concepts. Such conflicting information gives rise to the problems of exceptions and multiple inheritance during inheritance, and partial matching during classification. Although existing formalizations of inheritance hierarchies (e.g., those proposed by Etherington and Reiter, and Touretzky) deal adequately with exceptions, they do not address the problems of multiple inheritance and partial matching. This talk presents a formalization of inheritance hierarchies based on the principle of maximum entropy. The suggested formalization offers several advantages: it admits necessary as well as default attribute-values, it deals with conflicting information in a principled manner, and it solves the problems of exceptions, multiple inheritance, as well as partial matching. It can also be shown that there exists an extremely efficient realization of this formalization. 2:00 pm Tuesday, March 22 Unisys Paloi Research Center Route 252 and Central Ave. Paoli PA 19311 -- non-Unisys visitors who are interested in attending should -- -- send email to finin@prc.unisys.com or call 215-648-7446 --