Thanks for the encouragement!

I've found the following reference, but have had no luck in locating
a web-accessible copy-  

[Goldstein & Bobrow 1981] 
Ira P. Goldstein and Daniel G. Bobrow 
PIE: An Experimental Personal Information Environment 
Technical Report CSL-81-4, Xerox Palo Alto Research Center, 1981


Alan Kay wrote:
> 
> Les --
> 
> I think your POV on this (below) is a very good idea (and it has surfaced a
> number of times over the last 25 years or so without quite getting enough
> energy for a useful implementation). I believe that this approach really
> would amount to something, and concur with your speculations that replacing
> hierarchical inheritance with sideways "roles" (in the old days called
> "aspects" or "perspectives") would make things both simpler and more
> powerful. I was quite taken with the Goldstein and Bobrow approach in their
> PIE system built at PARC using Smalltalk-76.
>      A good place to start might be to reformulate the Morphic and end-user
> subsystems in Squeak into a rolebased model. For example, over the years,
> I've toyed with end-user objects that have the following roles:
> * a visible/graphic role
> * a collection/carrier role
> * a "participant in a simulation/app" role
> * a basic object role
> 
> As you note, it makes much more sense to have these be "sideways" than be
> hierarchical.
> 
> Cheers,
> 
> Alan
> 
> ---------
> 
> At 6:28 PM -0800 2/11/00, Les Tyrrell wrote:
> >Leandro Caniglia wrote:
> >>
> >> Les.--
> >>     I like your thoughts about using category
> >>     theory in Smalltalk!
> >>
> >> What do you mean with 'category theory'? Are you thinking
> >> about mathematical categories (objects, arrows, functors,
> >> etc)?
> >>
> >> /Leandro
> >
> >See Alek's message about that. Like I say in my own message,
> >I'm not that familiar with it, although Alek's comments
> >reminded me of something that I once had in mind.
> >
> >If you are wondering what I meant by my own comments, that
> >could be very different from category theory for all that I
> >know.  What I had in mind was making Roles into a part of
> >the normal Smalltalk model, alongside such things as Classes
> >and methods, and considering a different approach to building
> >classes that did not involve the classes having the inheritance
> >relationships, but rather having the Roles carry those.  Whether
> >that would ever actually amount to anything I have no idea.
> >
> >I think that this is possible in Squeak or VisualWorks because
> >about the only vm requirement for method lookup is that the method
> >dictionary be found in a particular slot of an object's "class".
> >Beyond that, there is almost no requirement that the "class" be
> >a, uh, "Class".  So, it could be a Role instead.
> >
> >I'm sure that there would be other problems with this- but then,
> >the notion is that as far as I the programmer know, I am composing
> >the class out of Roles.  The underlying mechanisms supporting
> >such a virtuality can be very different from what the programmer
> >percieves.
> >
> >-les