A bi-labeling based XPath processing system

Abstract

We present BLAS, a Bi-LAbeling based XPath processing System. BLAS uses two labeling schemes to speed up query processing: P-labeling for processing consecutive child (or parent) axis traversals, and D-labeling for processing descendant (or ancestor) axis traversals. XML data are stored in labeled form and indexed. Algorithms are presented for translating XPath queries to SQL expressions. BLAS reduces the number of joins in the SQL query translated from a given XPath query and reduces the number of disk accesses required to execute the SQL query compared with the traditional XPath processing using D-labeling alone. We also propose an approximate P-labeling scheme and the corresponding query translation algorithm to handle XML data trees that contain a large number of distinct tag names, and/or are very deep. This extension captures a spectrum of XPath-to-SQL query translation schemes, ranging from existing schemes that do not use P-labels to the one that uses exact P-labels. Experimental results demonstrate the efficiency of the BLAS system. t r a c tWe present BLAS, a Bi-LAbeling based XPath processing System. BLAS uses two labeling schemes to speed up query processing: P-labeling for processing consecutive child (or parent) axis traversals, and D-labeling for processing descendant (or ancestor) axis traversals. XML data are stored in labeled form and indexed. Algorithms are presented for translating XPath queries to SQL expressions. BLAS reduces the number of joins in the SQL query translated from a given XPath query and reduces the number of disk accesses required to execute the SQL query compared with the traditional XPath processing using D-labeling alone. We also propose an approximate P-labeling scheme and the corresponding query translation algorithm to handle XML data trees that contain a large number of distinct tag names, and/or are very deep. This extension captures a spectrum of XPath-to-SQL query translation schemes, ranging from existing schemes that do not use P-labels to the one that uses exact P-labels. Experimental results demonstrate the efficiency of the BLAS system.

Data Model Integration

“…The proposed techniques target a relational implementation but it can be used within native XML system too. Additionally, [24] presents BLAS [25] a BiLAbeling based XPath processing System, as a generic and efficient system for XML storage and XPath query processing by leveraging relational databases. Also, it represents algorithms for translating XPath query to SQL query.…”

XML query processing

“…PPFx overcomes this problem by introducing regular expression matching over appropriate suffices of rootto-node paths (Section 3.3.3.1). Another proposed structural encoding is BLAS [20] which also handles only child and descendant axes using two different labelling schemes. The key idea of BLAS is encoding each root-to-node path string into a PLabel arithmetic value substituting root-to-node path filtering with arithmetic range conditions.…”

“…Particularly, when a context element that is not nested to any previously read one is read -called root ancestor (rootAnc) -a descendant window is initialized (line 16). As long as following context elements are descendants of the last read rootAnc, these are kept in chain (lines [18][19][20]. We then check the structural relationship of each element fetched by the window with rootAnc and those kept in chain, by calling the regExprFilter() Athens University of Economics and Business, Department of Informatics method (line 9).…”