PosFilter: An Efficient Filtering Technique of XML Documents Based on Postfix Sharing

Abstract

XML message filtering is to evaluate the path matching of a large number of registered path queries over a continuous stream of XML messages in real time. For this purpose, YFilter system has been suggested to exploit the prefix commonalities that exist among path expressions. Sharing such commonality gives the benefit of improving filtering performance through the tremendous reduction in filtering machine size. However, postfix sharing also can be useful for an XML filtering situation. For example, if a stream of XML messages does not have any defined DTD (or XML schema), the XPath queries beginning with the ancestor-descendant axis (’//’) can be used often, e.g., ’//buyer/name’, ’//seller/name’, and ’//name’, and such query type is most likely to have the postfix sharing. Therefore, in this paper, we propose a bottom up filtering approach exploiting postfix sharing against the top down approach of YFilter exploiting prefix sharing. Some experimental results show that our method has better performance in the postfix-shared scenario.