A Computational Method for Defeasible Argumentation Based on a Recursive Warrant Semantics

Abstract

In a recent paper [2] the authors have formalized a recursive semantics for warranted conclusions in a general defeasible argumentation framework based on a propositional logic. The warrant recursive semantics is based on a general notion of collective (non-binary) conflict among arguments allowing to ensure direct and indirect consistency properties. This general framework has also been extended with levels of defeasibility and with a level-wise recursive definition of warranted and blocked conclusions. In this paper we focus on the recursive semantics for the particular framework of Defeasible Logic Programming (DeLP) extended with levels of defeasibility, called RP-DeLP, for which we characterize programs with a unique output (extension) for warranted conclusions, and we design, for this type of programs, an algorithm for computing warranted conclu- sions in polynomial space and with an upper bound on complexity equal to P^NP