Abstract. Consistent description and representation method of user interests are required for personalized Web applications. In this paper, we provide a formal definition and the "e-foaf:interest" vocabulary for describing user interests based on RDF/OWL and the FOAF vocabulary. As an application, under the framework of unifying search and reasoning (ReaSearch), we proposed interests-based unification of search and reasoning (I-ReaSearch) to solve the personalization and scalability requirements for Web-scale data processing. We illustrate how user interests can be used to refine literature search on the Web. Evaluation from the scalability point of view shows that the proposed method provides a practical way to Web-scale problem solving. Keywords. user interests, interest vocabulary, Web search refinement, unifying search and reasoning.