Systems and methods for streaming XPath query

An improved XML query system represents an XML document as a stream of discrete 'events,' with each event representing a portion of the document as the document is being parsed. Expression-based event matching such as XPath can be performed against the event stream using a stack to keep only the relevant contexts in memory. Observers can be used to listen for matching events. Matching events can then be routed for processing by appropriate objects or components and returned to the event stream if necessary. This description is not intended to be a complete description of, or limit the scope of, the invention. Other features, aspects, and objects of the invention can be obtained from a review of the specification, the figures, and the claims.