A Plausibility Semantics for Abstract Argumentation Frameworks
We propose and investigate a simple plausibility-based extension semantics for abstract argumentation frame- works based on generic instantiations by default knowl- edge bases and the ranking construction paradigm for default reasoning. 1 The goal of the present work is therefore to supple- ment existing instantiation efforts with a simple ranking- based semantic model which interprets arguments and at- tacks by conditional knowledge bases. The well-behaved ranking construction semantics for default reasoning (Wey 96, 98, 03) can then be exploited to specify a new exten- sion semantics for Dung frameworks which allows us to di- rectly evaluate the plausibility of argument collections. Its occasionally unorthodox behaviour may shed a new light on basic argumentation-theoretic assumptions and concepts. We start with an introduction to default reasoning based on the ranking construction paradigm. After a short look at abstract argumentation theory, we show how to interpret abstract argumentation frameworks by instantiating the ar- guments and characterizing the attacks with suitable sets of conditionals describing constraints over ranking mod- els. Based on the concept of generic instantiations, i.e. us - ing minimal assumptions, and plausibility maximization, we then specify a natural ranking-based extension semantics. We conclude with a simple algorithm, some instructive ex- amples, and the discussion of several important properties. 2 Ranking-based default reasoning