I think that the application of XML to things that are (a) large and
(b) subject to fancy statistical processing is a good idea mostly as
an *interchange* format. For doing heavy analysis, I would definitely
cram it into an RDBMS first. On the other hand, it's tough to exchange
3nf data reliably between systems, but trivially easy with XML, and
similarly easy to load/unload it to/from whatever fancy repository
you're using either end.
Also, for archiving it on tape, I think XML wins, because you have a
chance of still being able to read it in 10 years. -Tim