The Libferris Project is here:
http://witme.sourceforge.net/libferris.web/
This is related to the LarchFSIdea.
It presents a file-system type interface to a myriad
of data formats. Sadly, it's implemented as C++ IOStream
type calls as opposed to actually having OS support.
But, they've made some inroads and efforts in their approach
to canonicalization (to mangle a word) of extended attributes
of "files".
They also allow you to open up a "filesystem" as a DOM... and
thus apply XSLT scripts to it, etc.
-- PatrickStein - 04 Apr 2005