Message passing rather than object orientation
Marcel Weiher
marcel at metaobject.com
Sat Oct 13 11:07:00 UTC 2001
On Friday, October 12, 2001, at 02:43 PM, Alan Kay wrote:
> The main source of outside ideas was Dave Fisher's thesis (A
> Control Definition Language CMU 1970). This was not object-oriented
> (but I found it to be the logical complement to my thesis of the very
> same period) and Dave had cast it in terms of a McCarthy-like eval in
> itself, so it was very understandable. It had most of the things we've
> always wanted in messaging systems.
I obtained this particular thesis from CMU a while ago, and am still
somewhat unclear as to what in particular you are refering to. The only
thing I can think of is the "multiple sequential control" section.
> I think after Carl heard about Smalltalk in Nov 72, and saw some
> of the examples, he was able to come up with some valuable
> characterizations of control structures and objects. Unfortunately for
> posterity, neither the PARC group or the MIT group really was able to
> implement a practical enough version of the deeper scope of these
> ideas. (Part of the problem is that something like zero-overhead, large
> number of processes are needed to really do the job.)
Are these characterizations in the 77 paper? (Yet another one to hunt
down...)
> Recently Andreas Raab has done some remarkable experiments with very
> large numbers of very low overhead processes in Squeak which bodes well
> for the future.
I am still not quite sure for what specific problems large numbers of
processes are a good solution. Computing propagation patterns
on-the-fly and interleaved with the computation carried out by the
message payload may be one case, but many/most practical cases seem to
be solvable without the need for concurrency.
Marcel
--
Marcel Weiher Metaobject Software Technologies
marcel at metaobject.com www.metaobject.com
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