Schema-based Scheduling of Event Processors and Buffer Minimization for   Queries on Structured Data Streams
  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. 
Christoph Koch, Stefanie Scherzinger, Nicole Schweikardt, Bernhard   Stegmaier