A study of provability in defeasible logic

It is shown that defeaters do not add to the expressiveness of defeasible logic, among other results, and the analysis supports the restriction ofdefeasible logic to admit only acyclic superiority relations.

Abstract

Defeasible logic is a logic-programming based nonmonotonic reasoning formalism which has an efficient implementation. It makes use of facts, strict rules, defeasible rules, defeaters, and a superiority relation. We clarify the proof theory of defeasible logic through an analysis of the conclusions it can draw. Using it, we show that defeaters do not add to the expressiveness of defeasible logic, among other results. The analysis also supports the restriction of defeasible logic to admit only acyclic superiority relations.