Abstract. In previous work, we presented an RDFS ontology, based on the Argument Interchange Format (AIF), for describing arguments and argument schemes. We also implemented a pilot Web-based system, called ArgDF, for authoring and querying argument structures represented in RDF. In this paper, we discuss some of the limitations of our earlier reification of the AIF. We then present a new ontology which takes advantage of the higher expressive power of OWL. We demonstrate how this enables the use of automated Description Logic reasoning over argument structures. In particular, OWL reasoning enables significantly enhanced querying of arguments through automatic scheme classifications, instance classification, and inference of indirect support in chained argument structures. Keywords. Argumentation, Argument Interchange Format, Semantic Web, OWL