BFilter: Efficient XML Message Filtering and Matching in Publish/Subscribe Systems

XML message filtering and matching are important operations for the application layer XML message multicast. As a publish/subscribe system and a specific case of content-based multicast in the application layer, XML message multicast depends highly on the data filtering and matching processes. As the XML applications emerge, efficient XML message filtering and matching become more desirable. Many XML filtering techniques have been proposed in the literature. Most of those techniques do not address complex queries with predicates, twig patterns or branches; some require post-processing or a special coding scheme, which is either time consuming or becomes difficult for management for dynamic changes of user queries. This paper addresses the existing gap in the literature and proposes a new technique called BFilter which performs the XML message filtering and matching operation by leveraging branch points in both the XML publication document and user requests or queries. BFilter evaluates user queries that use backward matching branch points to delay further matching processes until branch points match in the XML publication document and the user query. Using the backward branch point matching technique, XML message filtering can be performed more efficiently as the probability of mismatching in the matching process is reduced. A number of experiments have been conducted and the results demonstrate that for complex queries, BFilter has a better performance than the well-known YFilter.