An algorithm of estimation pattern tree number in probabilistic XML data tree

Because of decomposition is a kind of effective strategy for query, the number of pattern tree in the probabilistic XML data tree is the basis of decomposing it. The definitions of absolute path vector and absolute path vector set are given. On the basis of parsing all absolute path in the probabilistic XML data tree, the algorithm for estimating the pattern tree number based on the absolute path vector set is presented. The experiment results show that the number of different scale pattern tree can be right estimated. The number of some different scale pattern trees should be estimated through the algorithm before decomposing, and it provides the rule of choosing one of some different scale pattern tree to decompose the probabilistic XML data tree.