This book constitutes the refereed proceedings of the 6th International XML Database Symposium, XSym 2009, held in Lyon, France, in August 2009 in conjunction with the International Conference on Very Large Data Bases, VLDB 2009.

The 8 revised full papers together with 7 short paper were carefully reviewed and selected from 26 submissions. Covering all current aspects of core database technology for XML data management, XML and data integration, and development and deployment of XML applications, the papers are organized in topical sections on XML twig queries, query execution, xml document parsing and compression, XQuery and XML transaction management and schema design.