The 9th International Conference on Extending Database Technology, EDBT 2004, was held in Heraklion, Crete, Greece, during March 14-18, 2004. The EDBT series of conferences is an established and prestigious forum for the exchange of the latest research results in data management. Held every two years in an attractive European location, the conference provides unique opp- tunities for database researchers, practitioners, developers, and users to explore new ideas, techniques, and tools, and to exchange experiences. The previous events were held in Venice, Vienna, Cambridge, Avignon, Valencia, Konstanz, and Prague. EDBT 2004 had the theme "new challenges for database technology," with the goal of encouraging researchers to take a greater interest in the current exciting technological and application advancements and to devise and address new research and development directions for database technology. From its early days, database technology has been challenged and advanced by new uses and applications, and it continues to evolve along with application requirements and hardware advances. Today's DBMS technology faces yet several new challenges. Technological trends and new computation paradigms, and applications such as pervasive and ubiquitous computing, grid computing, bioinformatics, trust management, virtual communities, and digital asset management, to name just a few, require database technology to be deployed in a variety of environments and for a number of di?erent purposes. Such an extensive deployment will also require trustworthy, resilient database systems, as well as easy-to-manage and ?exible ones, to which we can entrust our data in whatever form they are.

This book constitutes the refereed proceedings of the 8th International Conference on Extending Database Technology, EDBT 2002, held in Prague, Czech Republic, in March 2002.The 36 revised full papers presented together with six industrial and application papers, 13 software demos and one invited paper were carefully reviewed and selected from a total of 207 submissions. The papers are organized in topical sections on query transformation, data mining, XML, advanced query processing, moving objects, distributed data, distributed processing, advanced querying, XML-advanced querying, fundamental query services, estimation/histograms, and aggregation.