Adaptive Data Mediation over XML Data

The mediator/wrapper approach is used to integrate data from different databases and other data sources by introducing a middleware virtual database that provides high level abstractions of the integrated data. A framework is presented for querying XML data through such an Object-Oriented (OO) mediator system using an OO query language. The mediator architecture provides the possibility to specify OO queries and views over combinations of data from XML documents, relational databases, and other data sources. In this way interoperability of XML documents and other data sources is provided. Translation rules are defined that automatically generate an OO schema in the mediator database from the DTD of the XML documents, if available. A strategy is used for minimizing the number of types (classes) generated in order to simplify the querying. If XML documents without DTDs are read, or if the DTD is incomplete, the system extends the OO schema from the XML structure while reading XML data. As more XML data is read the OO schema is dynamically refined. This requires that the mediator database is capable of dynamically extending and modifying the OO schema. The paper overviews the architecture of the system and describes incremental rules for translating XML documents to OO database structures.