Holistic twig joins based on Sketch Tree

Due to the wide spread of XML and its importance, twig query matching, which has been identified as a core operation in querying XML data, has become a research hotspot. Although a number of algorithms have been proposed recently to process a twig query holistically, existing algorithms can be further improved with the help of the DTD file. In this paper, we (1) proposed the Sketch Tree structure according to the DTD scheme and employed it to translate the queries; (2) proposed a new labeling scheme named Sketch Dewey on the basis of the Sketch Tree to encode not only the elements in XML data but also the query; (3) designed an efficient path matching algorithm called PathCheck and a novel holistic twig join algorithm called TJumperJoin utilizing the Sketch Dewey code. To answer a query, they only need to scan the elements of leaf nodes in the query and benefitting from the Sketch Dewey labeling scheme, they can take advantage of bitwise operation to make acceleration. At last, extensive experiments are performed to examine the efficiency and effectiveness of our proposed techniques.