XML-based components for federating multiple heterogeneous data sources

Several federated database systems have been built in the past using the relational or the object model as federating model. This paper gives an overview of the XMLMedia system, a federated database system mediator using XML as federating model, built in the Esprit Project MIRO-Web. The system is composed of four main components: a wrapper generator using rule-based scripting to produce XML data from various source formats, a mediator querying and integrating relational and XML sources, an XML DBMS extender supporting XML on top of relational DBMSs, and client tools including a Java API and an XML query browser. The results demonstrate the ability of XML with an associated query language (we use XML-QL) to federate various data sources on the Internet or on Intranets.