Publish/subscribe systems offer a flexible way for information producers and information consumers to exchange data. In XML-based publish/subscribe systems, information producers publish XML documents and information consumers subscribe to documents of interest by specifying XPath expressions. The problem lies in XML filtering against large number of XPath expressions and routing the XML document throughout a network of XML routers to the interested consumers. This thesis proposes a novel algorithm for filtering XML documents against large numbers of XPath expressions. It encodes XPath expressions (XPEs) as ordered sets of predicates and translates XML documents into sets of tuples, which are evaluated over these predicates. For routing XML documents, the thesis introduces the advertisement, covering and merging techniques for XPath expressions, to reduce the amount of information required for storing routing state at each node in the network.