"Views: Moving the User Interface from the Application to the System"

[Massimo Dentico]

Another interesting UI system.
    http://www.cwi.nl/~steven/views/

In particular about "presentation invariants" (a sort of
constraints) see:

"Maintaining presentation invariants in the Views system"
    http://www.cwi.nl/ftp/CWIreports/AA/CS-R9262.ps.Z

Apparently no source available.

Regards.

-- 
Massimo Dentico