The Mediator EnvirOnment for Multiple Information Sources (MOMIS) aims at constructing synthesized, integrated descriptions of the information coming from multiple heterogeneous sources, in order to provide the user with a global virtual view of the sources independent from their location and the level of hetero-geneity of their data. Such a global virtual view is a con-ceptualization of the underlying domain and then may be thought of as an ontology describing the involved sources. In this article we explore the framework’s main elements and discuss how the output of the integration process can be exploited to create a conceptualization of the underly-ing domain