  The issue of representing attacks to attacks in argumentation is receiving an
increasing attention as a useful conceptual modelling tool in several contexts.
In this paper we present AFRA, a formalism encompassing unlimited recursive
attacks within argumentation frameworks. AFRA satisfies the basic requirements
of definition simplicity and rigorous compatibility with Dung's theory of
argumentation. This paper provides a complete development of the AFRA formalism
complemented by illustrative examples and a detailed comparison with other
recursive attack formalizations.
