Tech Reports

ULCS-07-003

Towards an Extensible Argumentation System

Adam Zachary Wyner and Trevor Bench-Capon

Abstract

Many types of inter-agent dialogue, including information seeking, negotiation and deliberation can be fruitfully seen as varieties of argumentation. Argumentation frameworks, originally introduced by Dung, provide a powerful tool for evaluating the sets of conflicting arguments which emerge from such dialogues. Originally argumentation frameworks considered arguments as completely abstract entities related by a single attack relation, which always succeeded. Use of the frameworks in practical application such as law, edemocracy and medicine, however, motivated a distinction between successful and unsuccessful attacks, determined by properties of the conflicting arguments. This remains insufficient, however, to capture a range of phenomena which can arise from procedural and contextual considerations, and which require that the success of an attack depend not only on the properties of the conflicting arguments but also on the nature of the attack or the context in which it is made. In this paper we present, in functional decomposition style, an analysis of arguments, their properties and relations which can accommodate a wide range of such phenomena. Our analysis is extensible and is presented in a series of stages which capture first the abstract notions of original argumentation frameworks, is then extended to embrace properties of arguments, and then further extended to include properties of relations between arguments. We illustrate each stage of this progression by representing characteristic systems of each type, and discuss the particular features of argumentation which they can address.

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