cf2 Semantics Revisited

Abstract argumentation frameworks nowadays provide the most popular formalization of argumentation on a conceptual level. Numerous semantics for this paradigm have been proposed, whereby cf2 semantics has shown to nicely solve particular problems concernend with odd-length cycles in such frameworks. In order to compare different semantics not only on a theoretical basis, it is necessary to provide systems which implement them within a uniform platform. Answer-Set Programming (ASP) turned out to be a promising direction for this aim, since it not only allows for a concise representation of concepts inherent to argumentation semantics, but also offers sophisticated off-the-shelves solvers which can be used as core computation engines. In fact, many argumentation semantics have meanwhile been encoded within the ASP paradigm, but not all relevant semantics, among them cf2 semantics, have yet been considered. The contributions of this work are thus twofold. Due to the particular nature of cf2 semantics, we first provide an alternative characterization which, roughly speaking, avoids the recursive computation of sub-frameworks. Then, we provide the concrete ASP-encodings, which are incorporated within the ASPARTIX system, a platform which already implements a wide range of semantics for abstract argumentation.