Abstract: In order to resolve the problem of semantic integration of heterogeneous relational databases, based on semantic Web technology, this paper focused on the query processing problem in ontology-based relational data integralion. An ontology-based integration infrastructure for heterogeneous relational databases was presented. To model different databases' schemas, we proposed an ontology-based data describing method. Ontology was used as the global schema to describe the semantic of relational schemas. A ctuery rewriting algorithm was provided, which can rewrite SPARQL query over global schema into local queries that can be executed on heterogeneous relational databases. The experiment showed that the approach we proposed has nice scalability.

Key words: Data integration, Relational database, Query rewriting, Ontology