Creating a Service-Oriented Architecture requires the identification of services to be composed together in order to solve a given need. Currently, software engineers perform this design task by hand by identifying services and how to compose them. In this paper, we propose RuGCo a system to automatically compose Web services coming from a static large repository, according to a domain ontology expressed in OWL, on the basis of a user query. The proposed system is not only able to find all suitable combinations of Web services, but also offers a visualization of the composition to let the software engineer inspect all possibilities.