Summary form only given. Recent research shows that ontologies are a prominent tool for the semantic interoperability of information sources. Unfortunately, semantic interoperability is not easy to achieve, as related knowledge is most likely to be described in different terms using different assumptions and different data structures. In this paper we provide an interoperability solution based on semantic mediation permitting to define a system of sharing, retrieving and transparent access to the heterogeneous information sources. The proposed approach is based on a multi-representation ontology specified in description logics extended by stamping mechanism. This solution provides a structured and shared vocabulary of several domains. This serves as support to a semantic mediator, to localize the necessary sources, analyze the request for distributed extraction of data and recompose the results in a user answer.