Efficient msubtree results computation for XML keyword queries

Abstract

In this paper, we focus on efficient constructing of matched subtree (MSubtree) results for keyword queries on XML data. We firstly show that the performance bottlenecks for existing methods lie in (1) computing the set of relevant keyword nodes (RKNs) for each subtree root node, (2) constructing the corresponding MSubtrees, and (3) parallel execution. We then propose a two-step generic top-down subtree construction algorithm, which computes SLCA/ELCA nodes in the first step, and parallelly gets RKNs and generates MSubtree results in the second step, where generic means that (1) our method can be used to compute different kinds of subtree results, (2) our method is independent of the query semantics; top-down means that our method constructs each MSubtree by visiting nodes of the subtree constructed based on an RKN set level-by-level from left to right, such that to avoid visiting as many useless nodes as possible. © 2013 Springer-Verlag Berlin Heidelberg.