Propositional Argumentation Systems vs Theorist

Propositional argumentation systems are based on assumption based reasoning and used for computing arguments which support a given hypotheses Assumption based reasoning is closely related to hypothetical default theories or inference through theory formation The latter approach known as the Theorist frame work has well known relations to abduction and default reasoning In this paper propositional argumentation systems are presented as an alternative to hypo thetical default theories and their relations to hypothetical default theories are explained The presented transformation from hypothetical default theories into propositional argumentation systems allows us to characterize all notions of hypo thetical reasoning in terms of argumentation systems The presented transforma tion is linear There exists also an inverse transformation which is partial in the sense that not all notions of propositional argumentation systems can be expressed in the framework of hypothetical default theories