We introduce an extension of the XQuery language, FluX, that supports event-based query processing and the conscious handling of main memory buffers. Purely event-based queries of this language can be executed on streaming XML data in a very direct way. We then develop an algorithm that allows to efficiently rewrite XQueries into the event-based FluX language. This algorithm uses order constraints from a DTD to schedule event handlers and to thus minimize the amount of buffering required for evaluating a query. We discuss the various technical aspects of query optimization and query evaluation within our framework. This is complemented with an experimental evaluation of our approach.

• Prof. Dr. Christoph Koch (Universit�t des Saarlandes)
• Dipl.-Inf. Stefanie Scherzinger (Universit�t des Saarlandes)
• Prof. Dr. Nicole Schweikardt (Humboldt-Universit�t zu Berlin)
• Dipl.-Inf. Bernhard Stegmaier (Technische Universit�t M�nchen)

• Online Demonstration
• For information on how to obtain our prototype implementation please contact one of the authors via e-mail.

• Christoph Koch, Stefanie Scherzinger, Nicole Schweikardt, and Bernhard Stegmaier
  Schema-based Scheduling of Event Processors and Buffer Minimization for Queries on Structured Data Streams
  Proceedings of the 30th International Conference on Very Large Data Bases (VLDB 2004),
  August 30 - September 3, 2004, Toronto, Canada, pp. 228-239
  Extended version: [CoRR]
  Errata: [TXT]
  Presentation: [PowerPoint]

• Christoph Koch, Stefanie Scherzinger, Nicole Schweikardt, and Bernhard Stegmaier
  FluXQuery: An Optimizing XQuery Processor for Streaming XML Data
  Demonstration at the 30th International Conference on Very Large Data Bases (VLDB 2004),
  August 30 - September 3, 2004, Toronto, Canada, pp. 1309-1312
  Poster: [PDF]

• The StreamGlobe Project (TU M�nchen)
• The XMLTaskForce Project project (TU Wien)