Compact Argumentation Frameworks
  Abstract argumentation frameworks (AFs) are one of the most studied
formalisms in AI. In this work, we introduce a certain subclass of AFs which we
call compact. Given an extension-based semantics, the corresponding compact AFs
are characterized by the feature that each argument of the AF occurs in at
least one extension. This not only guarantees a certain notion of fairness;
compact AFs are thus also minimal in the sense that no argument can be removed
without changing the outcome. We address the following questions in the paper:
(1) How are the classes of compact AFs related for different semantics? (2)
Under which circumstances can AFs be transformed into equivalent compact ones?
(3) Finally, we show that compact AFs are indeed a non-trivial subclass, since
the verification problem remains coNP-hard for certain semantics.
