Stéphane Rollandin wrote:
>> ...
> If #is: implementation has to reflect a class hierarchy, then I don't 
> see how it can be any better than #isKindOf: and #isMemberOf: 

In my opinion, it does not have to reflect a class hierarchy at all, but 
conformance to some protocol. Take a look at 
http://userweb.cs.utexas.edu/~wcook/Drafts/2009/essay.pdf .

Cheers,
Juan Vuletich