The Opaque project focuses on query optimization for relational XQuery engines. Advances in techniques for storage and query processing for XML using existing relational engines show that this approach has great potential for being able to manage the ever growing volumes of XML data. Many storage models, index structures, and algorithms have been proposed to speed up queries. Currently, attention is shifting towards query optimization techniques to address the remaining performance problems, to which this research hopes to make a contribution.
Go to OPAQUE homepage: http://www.ctit.utwente.nl/research/projects/national/nwo/open/opaque.doc