In the longer term I'm sure we will see XSLT processors that access XML
databases natively rather than relying on the input tree being in
primary memory: this is one reason why the synergy between XSLT and
XQuery is so important.

Your note raises the interesting perspective that in some years OS
might use mixed XML/RDBMS natively instead of a classic file system
for storing all kinds of information, in particular mail, documents,
spreadsheets and presentations.

What opportunities would arise from this? Would the benefits outweight
the cost?