query reformulation for an xml-based data integration system
The main objective of a mediator-based data integration system is to provide a unified view of several distributed and heterogeneous data sources. This view, called mediation schema, corresponds to a set of elements computed from data available on the local data sources. One of the biggest challenges facing a data integration system consists in answering a user query submitted in terms of the mediation schema given that the data is at the sources. This problem consists mainly in reformulating the query in terms of the source schemas and in integrating the corresponding answers. In this paper we address the problem of query reformulation in the context of an XML-based data integration system. Our solution is based on algorithms that generate a set of source queries considering a given user query and a set of mappings between the mediation schema and the data source schemas.
query reformulation data integration mediation xml