A proposal for a Unified Process for ONtology building: UPON 1 Antonio De Nicola * , Michele Missikoff * , Roberto Navigli ** * Istituto di Analisi dei Sistemi ed Informatica Consiglio Nazionale delle Ricerche Viale Manzoni, 30 – 00185 Roma { denicola, missikoff }@iasi.cnr.it ** Dipartimento di Informatica Università di Roma “La Sapienza” Via Salaria, 113 – 00198 Roma navigli@di.uniroma1.it Abstract. Ontologies are the backbone of the Semantic Web, a semantic-aware version of the World Wide Web. To the end of making available large-scale, high quality domain ontologies, effective and usable methodologies are needed to facilitate the process of Ontology Building. Many of the methods proposed so far only partly refer to well-known and widely used standards from other ar- eas, like software engineering and knowledge representation. In this paper we present UPON, a methodology for ontology building derived from the Unified Software Development Process. A comparative evaluation with other method- ologies, as well as the results of its adoption in the context of the Athena Inte- grated Project, are also discussed. 1 Introduction Ontologies, i.e. semantic structures encoding concepts, relations and axioms of a given domain, are the backbone of the Semantic Web (Berners-Lee et al., 2001), a semantic-aware version of the World Wide Web. Ontologies allow the web resources to be semantically enriched. This is a pre-condition to provide new, advanced ser- vices over the web, such as the semantic search and retrieval of web resources. Unfortunately the community has not yet reached a consensus on one or more stan- dard methods for building large-scale ontologies. For this reason, in this paper we propose a method derived from a well-established software engineering process, the Unified Software Development Process (Jacobson et al., 1999). Along this line, we present UPON, a novel approach to large-scale ontology build- ing that takes advantage of the Unified Process (UP). As a result, on one side, the adoption of the UP and the Unified Modeling Language (UML) makes ontology building an easier task for modellers familiar with these techniques. On the other side, 1 This work is partially supported by the Interop NoE and Athena IP, 6 th European Union Framework Programme.