An Accurate Identification of Extended XML Tree Pattern for XQuery Language

In order to utilize high-performance XML tree pattern query (TPQ) for implementing of XQuery language effectively, it is necessary to analysis the query plan and identify tree pattern from it. In this paper, we extend the functional intermediate language FXQL, which is used to implement XQuery language, with an extended XML generalized tree pattern representation (GTP++). Then, we propose an XML tree pattern identification approach, which is composed of a suit of query expression rewriting rules for extracting tree pattern and a GTP++ construction algorithm. Based on this approach, both explicit and implied propositional logic, various structural constraints and predicates can be extracted across nested query blocks in XQuery FLWOR expressions. The tree pattern identified by this approach is more holistic and precisely than previous methods. The approach expands the application of XML tree pattern query technology in the implementation of XQuery language. Experiments show its effectiveness and practicability.