RWTH Aachen University
Traditional optimizers fail to pick good execution plans, when faced with increasingly complex queries and large data sets. This failure is even more acute in the context of XQuery, due to the structured nature of the XML (eXtensible Markup Language) language. To overcome the vulnerabilities of traditional optimizers, the authors have previously proposed ROX, a Run-time Optimizer for XQueries, which interleaves optimization and execution of full tables. ROX has proved to be robust, even in the presence of strong correlations, but it has one limitation: it uses full materialization of intermediate results making it unsuitable for pipelined systems.