Abstract

One of the outcomes of the research work carried out on data integration in the last years is a clear architecture, comprising a global schema, the source schema, and the mapping between the source and the global schema. In this chapter, we study data integration under this framework when the global schema is specified in OWL, the standard language for the Semantic Web, and discuss the impact of this choice on computational complexity of query answering under different instantiations of the framework in terms of query language and form and interpretation of the mapping. We show that query answering in the resulting setting is computationally too complex, and discuss in detail the various sources of complexity. Then, we show how to limit the expressive power of the various components of the framework in order to have efficient query answering, in principle as efficient as query processing in relational DBMSs. In particular, we adopt OWL 2 QL as the ontology language used to express the global schema. OWL 2 QL is one of the tractable profiles of OWL 2, and essentially corresponds to a member of the DL-Lite family, a family of Description Logics designed to have a good trade-off between expressive power of the language and computational complexity of reasoning.

Citations