Hypermedia Dante Network (HDN) is an Italian National Research Project which aims to enrich the functionalities of the DanteSources Digital Library to efficiently represent knowledge about the primary sources of Dante's Comedy. DanteSources allows users to retrieve and visualize the list and the distribution of Dante's primary sources that have been identified by recent commentaries of five of Dante's minor works. Based on the DanteSources experience, the HDN project aims to formally represent the primary sources of the Divine Comedy. To reach this goal, we restructured and extended the DanteSources ontology to provide a wider and more complete representation of the knowledge concerning the primary sources of the Comedy. In this article we present the HDN ontology. The ontology is expressed in OWL and has as reference ontologies the CIDOC CRM and its extension LRMoo. We also briefly describe the semi-automatic tool that will be used by the scholars to populate the ontology