While the information published in the form of XML-compliant documents keeps fast mounting up, efficient and effective query processing and evaluation for XML have now become more important than ever. The query processor of a database system is the most critical component when it comes to performance and scalability. Structural join operations are central to evaluating queries against XML data, and are typically responsible for consuming a lion’s share of the query processing time. Thus, structural join order selection is at the heart of query optimization in an XML database, just as (value-based) join order selection is central to relational query optimization. XML is an emerging standard for data representation and exchange on the World-Wide Web. Due to the nature of information on the Web and the inherent flexibility of XML, much of the data encoded in XML will be semistructured, the data may be irregular or incomplete, and its structure may change rapidly or unpredictably. Our contribution can be understood as a roadmap that reveals desirable information and a theoretical perspective for an XML query processing, evaluation and query optimization.

1. T. Bray, J. Paoli, C. M. Sperberg-McQueen. "Extensible Markup Language (XML) 1.0". W3C Recommendation. Available at http://www.w3.org/ TR/1998/REC-xml-19980210, Feb. 1998.
2. Christian Mathis, Theo Härder "A Query Processing Approach for XML Database Systems". www.lgis.informatik.uni-kl.de/cms/fileadmin/users/mathis/.../gws2.pdf
3. C. Mathis and T. Harder. "A Query Processing Approach for XML Database Systems". 2005.
4. D. Maier. "Database Desire data for XML Query Language".http://www.w3.org/TandS/QL/QL98/pp /maier.html
5. J. Naughton et al. The Niagara Internet Query System. In IEEE Data Engineering Bulletin vol 24 issue 2. 2001
6. H. V. Jagadish et al. "A Native XML Database". In International Conference of VLDB. 2002
7. Dunren Che, Karl Aberer, M. Tamer Özsu. "Query optimization in XML structured-document databases". The VLDB Journal (2006) DOI 10.1007/s00778-005-0172-6. Published online: 28 April 2006 : Springer-Verlag 2005
8. Gottlob, G., Koch, C., Pichler, R.: "Efficient algorithms for processing XPath queries". In: Proceedings of VLDB, Hongkong, China (2002).
9. Chan, C.-Y., Felber, P., Garofalakis, M., Rastogi, R.: "Efficient filtering of XML documents with XPath expressions".In: Proceedings of International Conference on Data Engineering, San Jose, California, February 2002, pp. 235–244 (2002).
10. Su Cheng Haw, and G. S. V. Radha Krishna Rao. "Query Optimization Techniques for XML Databases". World Academy of Science, Engineering and Technology 22 2006.
11. M. Atay, Y. Sun, D. Liu, S. Lu, F. Fotouhi, "Mapping XML Data To Relational Data: A DOM-Based Approach", Proc. of the 8th IASTED International Conference on Internet and Multimedia Systems and Applications, 2004, pp. 59-64.
12. T.S. Chung, H-J Kim, "Techniques for the evaluation of XML queries: a survey", ACM Data and Knowledge Engineering 46, 2003, pp. 225-246.
13. M. Garafalakis, A. Gionis, R. Rastpgo, S. Seshadri, K. Shim, "XTRACT: a system for extracting document type descriptors from XML documents", Proceeding of the ACM SIGMOD Int. Conference on the Management of Data, 2000, pp. 165-176.

XML Database Query Processing Query Evaluation Query Optimization