On the one hand, if documents have been stored as native relational data
types, standard SQL queries allow fast access to high-volume data..
On the other hand, if documents have been stored as XML, one can apply XPath
expressions to filter the data returned by the relational data store.
Whenever the W3C XML querying language is implemented, XQuery will be available
from servers to apply XQueryX requests to native XML servers. However, as
of the autumn of 2003, this remaing "bleeding edge" technology.