Dear Squeakers,

(sorry for cross-posting; already posted to comp.lang.smalltalk)

For a piece of research I am currently working on, I have been
reviewing the arsenal of publications on the genealogy of Smalltalk(s)
for some hints on the origin of the
Smalltalk-specific "subclass responsibility" approach, i.e. the
Smalltalk dialect for "abstract object-classes",
roughly speaking. I am particularly interested in references to design
decisions. It would be particularly enlightening to know
whether the Xerox crew was aware of the "virtual quantity" feature
introduced in Simula-67 and their perception (beyond the mere difference 
with respect to type checking). I do have thoroughly
studied "original" Smalltalk-related contributions, far beyond the
Blue Book, but could not find explicit references beyond the mere fact
that this is the Smalltalk way of doing it; but why?

Note that I am well aware of more recent discussions on that very 
matter, especially in your community on the semantic consistency of
subclassResponsibility:

http://wiki.squeak.org/squeak/472

I am also aware of other language families that approach the idea of 
deferred-required implementation by means of a /placebo/ (what I would 
call it as a strategy).

Over at comp.lang.smalltalk, I was given as part of a more thorough answer:

> Because we also need a way to respond
> for the general case of a message received
> that is not understood. 

So, abstract super-classes are considered a special case deriving
from a more general issue.

Is anybody aware of some nuggets out there? I would be grateful for
any hint + your thoughts when looking at your languages' history ...

Best,
//stefan