The paper http://citeseer.nj.nec.com/jacob99software.html might be of
interest for those of you who do direct manip interfaces, as its ideas are
Basically, expressions like "mouse_down AND some_value < 2" can trigger state
changes inside an app-specific state transition diagram.
It employs a data-flow network, where "routes", that is, flows of variables
thru the network, are activated and deactivated depending on the current
A simple example: if the above expression yields true, a state change is
triggered, that activates a data-flow route from the mouse-position to some
I don't know if this is an old hat, but I think it's it very cool.