In recent years the research fifield of argumentation has become a major topic of artifificial intelligence [Bench-Capon and Dunne, 2007; Rahwan and Simari, 2009]. This is not only due to the intrinsic interest of this topic and recent applications (e.g. [Hunter and Williams, 2012]), but also because of fundamental connections to other areas of AI. In particular, the formal approach of abstract argumentation [Dung, 1995] has aroused much interest of research. A so-called abstract argumentation framework (AF) is a directed graph where nodes represent arguments and directed edges represent conflflicts between arguments, i.e. counter-arguments “attack” arguments by directed edges. The central question, given an AF F, is which sets of arguments can be jointly accepted. This is answered by argumentation semantics σ which give rise to extensions σ(F), i.e. sets of jointly acceptable arguments. A variety of extension-based semantics has been proposed over the years, an overview of these semantics and their properties can be found in [Baroni et al., 2011a]