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For further information on XQuery click here.
Besides these features of XQuery there is an extension called XQuery Update Facility which introduces some useful features to XQuery.
The XQuery Update Facility is a relatively small extension of the XQuery language which provides convenient means of modifying XML documents or data. As of March 14, 2008, the XQuery Update Facility specification has become a "Candidate Recommendation", which means it is now pretty stable.
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