Semantics for Evidence-Based Argumentation

The identification of consistent sets of arguments is one of the most important concerns in the development of computational models of argument. Such extensions drive the defeasible reasoning process. In this paper we present a novel framework that offers a semantics for argumentation-based reasoning grounded in an intuitive notion of evidence. In building this model of evidence-based argumentation, we first show how evidential support for and attack against one argument by multiple arguments can be represented. Secondly, we propose a new set of extensions, referred to as the evidential preferred, e-stable, and e-grounded extensions. These extensions are similar to those in Dung's original model, but are modified to cater for the notion of evidence. Our approach involves defining a new notion of attack, and showing how acceptability and admissibility follow on from it. These extensions capture the notion that an argument cannot be accepted unless it is supported by evidence, and will therefore increase the utility of argumentation as part of a reasoning system.