2. The method of claim 1 , wherein the hierarchically structured document is an Extended Markup Language Document and the update expression is an expression written in the XQuery programming language.
2. The method of claim 1 , wherein the hierarchically structured document is an Extended Markup Language Document and the update expression is an expression written in the XQuery programming language. 5. The method of claim 2 , wherein each base table row includes: a document identifier column uniquely identifying an Extended Markup Language document, and one or more Extended Markup Language columns storing information pertaining to the Extended Markup Language data for the Extended Markup Language document, wherein each Extended Markup Language column has a corresponding internal Extended Markup Language table storing the Extended Markup Language data.