On Wed, 2005-10-12 at 12:00 -0400, Stevan Little wrote: > Usefulness aside, why do Roles and Classes need to be seperate > beasts? In the current meta-model prototype, the role system is laid > atop the class system so that the following is true: > > Class is an instance of Class > Role is an instance of Class > Class does Role > > This then means that Role also .does Role since Role is an instance > of Class (which does Role). > > It gets very cyclical, but it essentially means that all classes can > be treated as roles. This allows for all sorts of interesting things > to happen actually.
I've always thought that classes were more specific than roles in that you can't apply a class to another class. (Maybe that's the wrong direction of specificity. Though I am positive that .does() is more general than .isa(), I always have to stop and think about which direction co- and contra-variance goes.) Certainly I think declaring a class should imply a role of the same name, even if you can't actually apply that role and mix in state and behavior. > I have to admit though, that this comes directly from Scala (so maybe > we are not alone here out on the edge :) I've also heard that Sather does something similar but don't know any details. -- c
