Label Size Increment of Bit String Based Labeling Scheme in Dynamic XML Updating

XML query processing based on labeling schemes has been proposed in the past several years. Based on labeling schemes, the structural relationships between XML nodes can be directly determined without the need of accessing the XML document. However, the existing labeling schemes have to re-label the pre-existing XML nodes or re-calculate the label values when a new node is inserted into the XML tree during an updating process. EXEL as a bit string based encoding and labeling scheme is able to remove the process of re-labeling for the pre-existing XML nodes efficiently. However, EXEL is unable to reuse the deleted labels for future node insertions. Also, another problem of EXEL is in the frequent skewed insertions where nodes always are inserted at a fixed place of an XML tree. In this case, the label size increases significantly. In this paper, we propose an algorithm to reuse the deleted labels for future node insertions and propose a strategy to solve the problem of frequent skewed insertion. The experimental results show that the proposed algorithm can reuse all the deleted labels for future insertions. Also, the proposed strategy can reduce the increment of label size in the case of frequent skewed insertions efficiently.