Defeasible inheritance through specialization

Typed substitution provides a means of capturing inheritance in logic deduc tion systems. However, in the presence of method overriding and multiple in heritance, inheritance is known to be nonmonotonic, and the semantics of pr ograms becomes a problematic issue. This article attempts to provide a gene ral framework, based on Dun,ss argumentation theoretic framework, for devel oping a natural semantics for programs with dynamic nonmonotonic inheritanc e. The relationship between the presented semantics and perfect-model (with overriding) semantics: proposed by Dobbie and Topor (1995), is investigate d. It is shown that for inheritance-stratified programs, the two semantics coincide. However, the proposed semantics also provides correct skeptical m eanings for the programs that are not inheritance-stratified.