MLTwig: A Multi-Layer Tree Pattern Matching Approach for XQuery

Twig query, also known as tree pattern query (TPQ), is considered as the core operation of XML data queries. However, a complex XML query described by XQuery often cannot be represented by a single basic TPQ. Aiming at XQuery language, this paper presents a multi-layer tree pattern representation method, named MTP, and a matching algorithm MLTwig, which can effectively use intermediate results of outer query to match inner tree pattern in MTP based on a novel data structure, WTree, thereby saving time and space. Experimental results show that this algorithm can improve the processing efficiency for XQuery expression which can be represented by MTP.