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Section: Research Program

Advanced Algorithms for Efficient XML processing

The development of Web technologies has led to a strong increase in the number and complexity of the applications which represent their data in Web formats, among which XML is used for structured documents. To manipulate very large volumes of XML data in a declarative fashion, the XQuery XML query language has been standardized by the W3C and is by now quite widely supported in industrial systems and research prototypes. The XQuery language allows expressing highly complex queries featuring complex navigation, joins, and nesting; the latest XQuery 3.0 has been extended with powerful grouping functionalities, too. For all these reasons, the efficient evaluation of XQuery queries and updates on large XML databases remains a challenge.

To address this challenge, the team specializes in two orthogonal performance enhancement techniques. The first one concerns the optimization of XML stores, in order to reduce as much as possible one of the main components of query evaluation cost, namely accessing the data. The second is static analysis of queries and updates, based on type systems; from a performance perspective, such static analysis techniques allow increasing parallelism, detecting operations whose results are not needed and thus whose evaluation can be omitted, etc.