On Sandewall's paper: Nonmonotonic inference rules for multiple inheritance with exceptions

摘要

Sandewall (1986) presents a theory of multiple inheritance with exceptions (also called non- monotonic inheritance) based on a set of nonmonotonic inference rules, taking advantage at the same time of theories based on nonmonotonic logic as proposed by Etherington and Reiter and of path-based theories as proposed by Touretzky, Horty and Thomason. Flaws in Sandewall's set of rules are shown and a revised set of rules is proposed. This revised set is shown to provide the same conclusion sets on a hierarchy as path-based theories for three classical variants of preclusion. Moreover, although most approaches to inheritance leave it in the metalanguage, it is shown that putting preclusion in the object language provides extensions with desirable general properties which are not always true in the restricted language of conclusion sets.