As more and more data becomes available in XML format, a general purpose XML repository management system (XRMS) is needed. Rather than developing it from scratch, there is great interest to exploit existing relational database technology as backend engine to store, retrieve, and query XML data set due to its maturity and performance.

    However, due to the mismatch between the complexity of semi-structured XML data model and the simplicity of flat relational model, there are many ways to store one document in a relational database, and a number of heuristic techniques need to overcome. These include the data model mapping strategies, the transformation of XML queries into SQL queries, XML order handling, XML update propagation, XML query optimization, and XML indexing.

    The Rainbow System we are proposing is based on a flexible strategy of mapping XML to the relational data model using generic XQuery loading statements, supports optimized XML order-sensitive query processing via an XML Query Algebra, XQuery to SQL translation, and serve as a solid yet scalable foundation for extended XML-based applications.

    Specific next research goals within the larger Rainbow project that we are targeting include Update Query Processing through the XML virtual Views, Incremental XML view maintenance, XQuery Multiple Query Optimization, and XML Query Optimization by exploiting Materialized XML Views.