Argument representation for editorial text

摘要

This paper presents a theory of argument representation for computer comprehension of editorial text. The theory has been implemented in a prototype system called OpEd, which reads politico-economic editorials and answers questions about their contents. The theory characterizes five major classes of knowledge structures: beliefs, attack relationships, support relationships, argument units (AUs), and meta-argument units (meta-AUs). During editorial comprehension, OpEd represents explicitly the beliefs of the editorial writer and his/her implicit opponents. Beliefs involve predictions about goals, plans, events, and states. Three types of predications are distinguished: evaluations about plans, causal relationships, and beliefs about beliefs.Beliefs in an editorial are involved in support relationships or attack relationships. An attack is a relationship between two beliefs whose contents involve mutually-exclusive planning situations or opposite effects of a plan on interrelated goals. A support is a relationship that consists of a belief, the justification for the belief, and a warrant (itself a belief) that connects a belief to its justifications. Belief justifications are based on refinements of plan evaluations, refinements of plan-goal relationships, analogies, and examples.Beliefs, attack relationships and support relationships are organized by AUs, which encode language-free and domain-free knowledge about argument structure and content. With the aid of domain-specific knowledge, AUs can be instantiated to model arguments in which an arguer refutes his/her opponent's position that a given plan should/should not be used. Arguments about arguments are represented as meta-AUs, which specify argument errors that result from either inconsistencies between actions and beliefs, or support strategies involving plausibilities, circularities, self-contradictions, or shifts on the burden of proof. Meta-AUs are represented in OpEd as attacks on warrants and are used to model discussions about the nature of valid reasoning.