"Andreas Raab" <andreas.raab at gmx.de> wrote in
> Trygve Reenskaug wrote:
>> A role is played by an object at run time. This object can be an instance 
>> of any class that implements its trait. So the trait is tied to a 
>> fundamental abstraction that is on the same level as the class.
>
> Interesting. But aren't you describing interfaces?

The role itself is better compared to a variable than to an interface. The 
corresponding trait can provide an interface definition, as well as an 
implementation that refers to other related roles. I think Trygve figured 
out a way to extend the compiler so that the method bodies (typically in 
traits, I expect) can use distinguished "Role variables", which the compiler 
translated into a dynamic lookup query.

My 2c guesses :-)

Sophie