Document Structure Description (DSD)

The discussion of CSS reminded me of some long-ago work that used CSS 
selectors and processing as a basis for a schema language.  It doesn't 
always get mentioned in the list of early schema languages, but it's worth 
exploration for those of us still looking for interesting new ideas in the 
schema space.

The CSS-inspired version is at:
http://www.brics.dk/DSD/specification.html

I was happy to also see a more recent version, though it seems to have left 
its CSS ancestry behind:

http://www.brics.dk/DSD/

There are some interesting aspects to it, particularly (to me) its use of 
regular expressions and its whitespace normalization rules.