High-Performance XML Filtering: An Overview of YFilter

We have developed YFilter, an XML filtering system that provides fast, on-the-fly matching of XML-encoded data to large numbers of query specifications containing constraints on both structure and content. YFilter encodes path expressions using a novel NFA-based approach that enables highly-efficient, shared processing for large numbers of XPath expressions. In this paper, we provide a brief technical overview of YFilter, focusing on the NFA model, its implementation, and its performance characteristics.