Abstract: As increasing amounts of information arc stored, exchanged, and presented using XMI，the ability to query XML data sources becomes increasingly important in XML database field. The flexibility and complexity of XQuery language are the great challenge to XQuery implementation. High-performance implementation of XQuery needs to use query optimisation methods provided by XMI. query algebra, also needs to use efficient holistic twig matching algorithm. This paper presented a basic architecture of XQuery implementation, and then gave an overview of the current status of two key technology for native XQuery implementation-XMI. query algebra and tree pattern matching. Finally, this paper prospected future research directions and presented some viewpoints of XQuery implementation.

Key words: XML, XQuery language, Query algebra, Tree pattern