XML-twig approximate matching twig join algorithm based on DTD

Recently, the majority of twig join algorithms have been proposed are based on matching querying given by the user strictly. That is to say, matching with high accuracy between the query and the data specified. For some simple queries, such as the queries only containing target path, though the user´s final purpose is clear, the middle path may be ambiguous. Such kind of target path query which doesn´t contain branches can be implemented by the twig join algorithm which has already been proposed, such as PackStack, TwigStack, TJFast.. However, if the user expressed the middle path of the twig query ambiguously, the results of the above join algorithms would be empty. Therefore, strict matching algorithms are not always perfect. In this paper, we propose XML-twig target path approximate matching twig join algorithm based on DTD named FTJ, which can realize flexible matching. It does not only meets the strict matching, but also satisfies the query needs with clear query target when the user doesn´t understand the pattern information of the DTD.