OWL 2 Virtual Integration System

We have built a virtual data integration system which extends the BIRN Mediator[1] to include OWL 2 ontologies where these ontologies are used as domain schema. This mediator integrates data from multiple, heterogeneous sources. This data integration system rewrites conjunctive queries using LAV views defined over a DL-Lite ontology. This is an important problem in query optimization, data integration and ontology-based data access. The mediator presents to users a unified domain ontology defined in DL-Lite. However, the mediator contains no data, all the data remains at the sources. Each source may have a different schema. We define LAV logical mappings from each source to the mediator's domain ontology. Given a conjunctive user query, our mediator first rewrites it into a union of conjunctive queries (UCQ), which captures the inferences implied by the DL-Lite ontology, using REQUIEM[2]. Second, the mediator rewrites this domain UCQ, using the source mappings, into a UCQ over the source schemas. Third, this UCQ over the source schemas is converted into a SQL query and is evaluated via OGSA-DAI resources and is sent to the MySQL database via the query execution engine.