A Path-Based Labeling Scheme for Efficient Structural Join

The structural join has become a core operation in XML query processing. This work examines how path information in XML can be utilized to speed up the structural join operation. We introduce a novel approach to pre-filter path expressions and identify a minimal set of candidate elements for the structural join. The proposed solution comprises of a path-based node labeling scheme and a path join algorithm. The former associates every node in an XML document with its path type, while the latter greatly reduces the cost of subsequent element node join by filtering out elements with irrelevant path types. Comparative experiments with the state-of-the-art holistic join algorithm clearly demonstrate that the proposed approach is efficient and scalable for queries ranging from simple paths to complex branch queries.