The recent developments of Computer and Telecommunication technology, such as the expansion of the Internet and the World Wide Web, have made available to users a huge number of information sources, generally autonomous, heterogeneous and widely distributed. As a consequence, information integration has emerged as a crucial issue in many application domains, e.g., distributed databases, cooperative information systems, data warehousing, as well as in accessing distributed data over the web.

In this paper we present DIS@DIS1, a state-of-the-art system for semantic data integration, that is capable of reasoning about integrity constraints in order to improve query answering. As usual in data integration systems [9, 5, 8], DIS@DIS provides a uni.ed view of different sources, called global schema, which can be queried by the user. Thus, the user does not interact with the sources, but gets reconciled information through the system that is in charge of accessing relevant sources and retrieving requested data.