Refined Preference-based Argumentation Frameworks

Argumentation is a reasoning model based on constructing arguments, determining potential conflicts between arguments and determining acceptable arguments. Dung's argumentation theory is an abstract framework based on a binary defeat relation between arguments. Due to this abstract representation, it has been instantiated in different ways. In particular, preference-based argumentation frameworks take into account a preference relation over arguments together with a (non necessarily symmetric) attack relation. We show that preference-based argumentation frameworks faithfully instantiate Dung's framework only when the attack relation is symmetric. Moreover the latter condition prevents undesirable results. We also promote a higher impact of preferences in preference-based argumentation frameworks and propose different ways to rank-order sets of acceptable arguments.