The Optimization of Complex XML Queries over XML Streams under DTD

Time and Space complexity is a critical factor for a successful stream-based continuous query processing system. In this paper, we address the optimization of complex XML queries over XML Streams by using the semantic and structural constraints of its DTD. The optimization is preprocessed before the runtime of matching XML stream against user's queries in order to simplify XPathes. An approach that processes complex twig patterns with OR-predicates and AND-predicates over XML document streams is also described in this paper, which can be also be used without DTDs.