The main purpose of building data integration systems is to facilitate access to a multitude of data sources. A data integration system must contain a module that uses source descriptions in order to reformulate user queries which are posed in terms of the composite global schema, into sub-queries that refer directly to the schemas of the component data sources. In this paper we propose a method for this user query translation task to target distributed heterogeneous structured data residing in relational databases and semi-structured data held in well-formed XML documents (XML documents which have no referenced DTD or XML schema) produced by Internet applications or human-coded. These XML documents can be XML files on local hard drives or remote documents on Web servers. Our method is based on mappings between the master (composite) view and the participating data source schema structures that are defined in a generated XML Metadata Knowledge Base (XMKB).
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