Almost all current database systems offer tools to export or view its content as XML which is also accepted as the emerging standard for promoting data interoperability over the web. However, XML focuses only on the syntax of data instead of the semantic and at the same time users get full freedom to model XML sources according to their local requirements. Consequently, these sources of the same domain adapt to different structures may represent data with similar semantic. In our work, we concentrate on integrating (interoperating) heterogeneous XML sources of the same domain to eliminate the structural differences of the user queries (accessing these sources) while they represent similar semantic. In this paper, we proposed architecture of semantic mediation approach based on OWL ontology. We also highlight how we can take the profit of OWL for integrating local ontologies that will be a great help for the completion of our architecture.