Processing XML View Queries Including User-defined Foreign Functions
Yoshiharu Ishikawa, JUN KAWADA, Hiroyuki Kitagawa · Web Information Systems Engineering · 2002
With the increased popularity of XML, XML publishing ofRDBs has been attracting a lot of research interests. One oftypical approaches is to use a middleware system to renderXML views over RDBs and to allow users to access data withXML query languages such as XQuery. The query processingis done efficiently by making the best of the querying powerof RDBMSs. Namely, XML queries are translated into SQLqueries and tagging operations, which are processed by theRDBMSs and middleware, respectively. In some XML querylanguages including XQuery, use of user-defined foreign functionsis enabled or planned as an extension feature to cope withdomain dependent semantics. Foreign functions are defined forXML fragments, and their implementations are often given bycodes in a general programming language. The existing queryprocessing schemes on XML views do not consider cases whereforeign functions are included in XML queries. In this paper,we propose extended schemes to process XML queries in suchcases. In the proposed schemes, the middleware takes careof processing foreign functions as well as tagging operations.Therefore, the proposed schemes are applicable to XML viewson commonly available RDBMSs. Three types of query processingschemes are proposed, and their performance is studiedwith experiments.