I've just stumbled upon a new article at xml.com: Directory Trees to Document Trees. I've posted a comment to the article and dropped a note to the author.
Here is my comment:
As the article mentions XML representation of a file system, I think that the following link is of high relevance and interest:
find with XPath over file system
The standard UNIX utility find now supports XPath:$ ./find -xpath '/bin/*[@size > /bin/bash/@size]' /bin/ipv6calc /bin/rpm
The author is John E. Simpson. His homepage is http://www.flixml.org/. Unfortunately, for some reason, the start page is empty. With words similar to the above, I notified him about the my development.