QUERY FORMULATION AND EVALUATION FOR XML DATABASES Kiyoshi Akama Center for Information and Multimedia Studies, Hokkaido Unversity, Sapporo 060, Japan akamal!!cims.hokudai.ac.jp Chutiporn Anutariya Department of Telematics, Norwegian University of Science and Technology, N-7491 Trondheim, Norway Chutiporn.Anutariyal!!item.ntnu.no Vilas Wuwongse Computer Science & Information Management Program, Asian Institute of Technology, Pathumtani 12120, Thailand vw<llcs.ait.ac.th Ekawit Nantajeewarawat Information Technology Program, Sirindhorn International Institute of Technology, Thammasat University, Pathumtani 12120, Thailand ekawitl!!siit.tu.ac.th Abstract The proposed approach to XML query formulation and evaluation de- veloped by means of XML Declamtive Description (XDD) theory for- malizes a query as an XDD description comprising one or more XML clauses the syntax of which can be subdivided into the three specifi- cations: pattern of XML elements to be selected, the query's selection criteria and the structure of the resulting elements. It supports for- mulation of essential functionality requirements for an XML query lan- guage such as selection and extraction, combination, transformation, closure and nested queries. Evaluation of a query on a specified XML database is carried out by employment of Equivalent 'I'ransformation paradigm. Moreover, since XDD theory provides a simple mechanism for representation of knowledge and relationships among elements in a The original version of this chapter was revised: The copyright line was incorrect. This has been corrected. The Erratum to this chapter is available at DOI: 10.1007/978-0-387-35616-7_23 © IFIP International Federation for Information Processing 2002 W. Cellary et al. (eds.), Internet Technologies, Applications and Societal Impact