This book constitutes the refereed proceedings of the 5th International XML Database Symposium, XSym 2007, held in Vienna, Austria, in September 2007 in conjunction with the International Conference on Very Large Data Bases, VLDB 2007.

The 8 revised full papers together with 2 invited talks and the extended abstract of 1 panel session were carefully reviewed and selected from 25 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 XPath query answering, XQuery evaluation and performance, as well as XML updates, temporal XML data and concurrency.

This book constitutes the refereed proceedings of the 4th International XML Database Symposium, XSym 2006, held in conjunction with the International Conference on Very Large Data Bases, VLDB 2006. The book presents 8 revised full papers, focused on building XML repositories and covering query processing, caching, indexing and navigation support, structural matching, temporal XML, and XML updates. Topical sections include query evaluation and temporal XML, XPath and twigs, and XML updates.

This yearmarks anexciting time in the XML-database space: XQueryis moving closer to becoming a full W3C Recommendation, and the "Big 3" database vendors (IBM, Oracle, Microsoft) are expected to release XQuery support in theirrelationalDBMSs, joininganumberofexistingopensourceandcommercial products. Thus, we are very pleased to feature an industrial paper (describing theXML-speci?cfeaturesofMicrosoftSQLServer)aswellas14researchpapers. XSym's focus this year was on building XML repositories, and papers discussed the following topics: indexing support for the evaluation of XPath and XQuery; benchmarks and algorithms for XQuery and XPath evaluation; algorithms for constraint satisfaction checking, information extraction, and subtree matching; and applications of XML in information systems. This year, XSym also coordinated its e?orts with the Database and P- gramming Languages Symposium, DBPL 2005. The resulting program included not only presentations of the papers in this proceedings, but also a joint DBPL- XSym keynote talk by Giuseppe Castagna, developer of the CDuce language for XML processing, and a joint panel on open XML research problems and challenges. The organizers would like to express their gratitude to the XSym Program Committee and external reviewers for their e?orts in providing very thorough evaluationsofthesubmittedpapersundersigni?canttimeconstraintsandto- crosoftfortheirsponsorshipandfortheuseoftheMicrosoftConferenceMana- ment Toolkit. We would also like to thank Gavin Bierman and Christoph Koch, the organizersof DBPL, for their e?orts andtheir willingness to coordinate with us. These proceedings are dedicated to Alberto Mendelzon who sadly passed awaythisyear.Asastrongsupporterofandactivecontributortothissymposium series he will always remain in our memory.

Since its first edition in 2003, the XML Database Symposium series (XSym) has been a forum for academics, practitioners, users and vendors, allowing all to discuss the use of and synergy between database management systems and XML. The previous symposia have provided opportunities for timely discussions on a broad range of topics pertaining to the theory and practice of XML data management and its applications. XSym 2009 continued this XSym tradition with a program consisting of 15 papers and a keynote shared with the 12th International Symposium on Database Programming Languages (DBPL 2009). We received 26 paper submissions, out of which eight papers were accepted as full papers, and seven as short/demo papers. Each submitted paper underwent a rigorous and careful review by four referees for long papers and three for the short ones. The contributions in these proceedings are a fine sample of the very best current - search in XML query processing, including full text, keyword and loosely structured queries, stream querying and joins, and materialized views. Among new theoretical advances we included work on a lambda-calculus model of XML and XPath, on m- ping from the enhanced entity-relationship conceptual model to the W3C XML Schema Language, on transactions, and extensions to XPath. Finally, work on data parallel algorithms, compression, and practical aspects of XQuery, including query forms and the use of Prolog are also part of this volume.