Wanted: Comparison of XML-based Query and Table-based SQL

Jon Udell writes about XML for the Rest of Us wherein Adam Bosworth writes...

"The relational database is designed to serve up rows and columns," said BEA's Adam Bosworth in his keynote talk. "But our model of the world is documents. It's 'Tell me everything I want to know about this person or this clinical trial.' And those things are not flat, they're complex.

I agree with the idea of semi-structured searching and manipulations. But I don't expect anyone would deny we still need traditional (e.g. business) calculations and those will be well served by more structure than less. I'd like to see a more direct XML Query and SQL comparison. As it stands, I'm being led to believe I'll should use XML Query (i.e. something with XPath-like stuff in it) for doing non-numerical property-tree searches over data that has been or could be expressed in an XML text; but I should use SQL for doing relationally flat table-column calculations over data that has been entered into a relational database.

There is a merger out there somewhere that I'm not seeing, or maybe just an example of what such a merger might look like.