Storage consumption of variable-length XML labels uninfluenced by insertions

In recent years, the method of assigning labels to the nodes of an XML tree is getting more attraction. Various functions in an RDBMS can be easily utilized by storing the labeled XML documents into the RDB. However, in traditional labeling methods, a number of nodes need to be relabeled, when the XML documents are updated. To address this problem, we proposed DO-VLEI code combining VLEI code with the Dewey Order method. DO-VLEI code is effective to reduce the update cost, but the label size increases rapidly when handling large XML documents. To reduce the label size, we presented Compressed-bit-string DO-VLEI (C-DO-VLEI) code. However, it is difficult to handle the length of C-DO-VLEI because it is a variable-length code. In this paper, we propose two effective methods, VLEI-ABL and VLEI-EOL for handling the code length of C-DO-VLEI. We perform experiments to compare the storage consumption of the proposed methods with the previously known ORDPATH. The experimental results show that our methods considerably outperform the ORDPATH.