In this paper we present an ontology-based data management (OBDM) project concerning the Italian public debt domain, carried out within a joint collaboration between Sapienza University of Rome and the Department of Treasury of the Italian Ministry of Economy and Finance. We discuss the motivations at the basis of this project and present the main characteristics of the ontology we have built. We also describe the mechanisms we used to link the ontology to the actual data and the tools we have adopted for supporting ontology development and maintenance, as well as exploiting OBDM services. Finally, we provide a thorough evaluation of the ontology we produced and discuss in detail the role that it plays within the whole information system of the ministry department responsible for managing Italian public debt data.