Norms and Extended Argumentation Frameworks

This paper discusses reasoning about norms using Extended Argumentation Frameworks. We argue that norms emerge from a process of value based practical reasoning. We model practical reasoning using Action Based Alternating Transition Systems with Values, with the resulting arguments evaluated in an Extended Argumentation Framework, which permits arguments to attack attacks as well as arguments, and so provides a natural way of representing exceptions. Following our consideration of how norms are justified, we consider their application. Our representation of norms in EAFs enables us to offer an accessible account of permissions and exceptions. We illustrate our approach with an example relating to some US Supreme Court Fourth Amendment cases.