Faceted Queries in Ontology-based Data Integration

The aim of using ontology-based data integration is to provide users with a unified view, in a form of a global application domain ontology, over a multitude of data sources. The terminological component of this ontology is then presented as the global schema of the system and is used as the reference model for formulating queries. The extensional knowledge consists of RDF data sets (graphs) stored in local databases. In such scenario, a faceted query interface is a desired solution for end-user data access. Then there is a need for effective query answering utilizing both extensional and intentional knowledge representation. In this paper, we propose and discuss a possible solution to this issue. We show how a class of deductive rules, in particular Datalog rules and rules defining functionality, can be incorporated in the process of ontology-enhanced query answering in ontology-based data integration systems.