Tech Reports

ULCS-07-002

Precedent and Procedure: an argumentation-theoretic analysis

Adam Zachary Wyner and Trevor Bench-Capon

Abstract

In theoretical AI, much recent research on arguments treats them as entirely abstract, only related by an attack relation, which always succeeds unless the attacker can itself be defeated. However, this does not seem adequate for legal argumentation. Some proposals have suggested regulating attack relations using preferences or values. However, this does not explain how an audience can prefer or value an argument, yet be constrained by the procedure of debate not to accept it. Nor does it explain how certain types of attack may not be allowed in a particular context. For this reason, evaluation of the status of arguments within a given framework must be allowed to depend not only on the attack relations along with the intrinsic strength of arguments, but also on the nature of the attacks and the context in which they are made. In this paper we present a formal, functional decomposition style, description of arguments articulated into their component parts and contexts which allows us to represent and reason with types of attacks with respect to context. This machinery allows us to account for a number of factors currently considered to be beyond the remit of formal argumentation frameworks.

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