Model Based Critique of Justifications for Action

Justifications for actions can typically be critiqued on a number of grounds. Critiques of such justifications can be structured using an argumentation scheme for practical reasoning and associated critical questions. The form that the critiques can take in a computational system, however, depends crucially on the semantic underpinnings of the scheme. We describe a semantic model which, we argue, can support a rich and systematic critique of justifications for actions presented using a argumentation scheme specifically designed to support practical reasoning. The approach has been realised as a Prolog program, and the paper is illustrated by a running example and fragments of the code for the application.