One of the things I’ve added to my "Things to tinker with when I get time" list is this ECO add-on from Thailand:

Centillex EcoAccess is a free library to enable declarative data access services for Borland ECO. It provides flexibilities to declare methods for querying or accessing ECO objects via OCL expression.

OK, so that meant bugger all to me as well when I read it, but looking at the code in the tutorials on the site, it makes a bit more sense.
Still not sure if I’d use it or not, but their use of attributes has got me curious. Worth a couple of hours playing with it to see, I think.