The Development of a "Logic of Argumentation"

A recurring problem with the development of decision support systems in medicine is the difficulty of eliciting precise numerical uncertainty values for large fragments of the domain. A prototype information system for general practitioners, the Oxford System of Medicine (OSM), addressed this problem by using an informal mechanism of argumentation. Arguments supporting and opposing the propositions of interest were identified when numerical uncertainty values where unavailable. We propose, in this paper, a proof theoretic model for reasoning under uncertainty which is motivated by the need to provide a formal underpinning for the OSM inference engine. As well as giving a presentation of a “Logic of Argumentation” (LA) as a labelled deduction system, we also discuss the development of a category theoretic semantics for LA.