prototypes vs classes was: Re: Sun's HotSpot

Alan Kay alank at
Sat Oct 10 04:40:35 UTC 1998

Folks --

Just a gentle reminder that I took some pains at the last OOPSLA to try to
remind everyone that Smalltalk is not only NOT its syntax or the class
library, it is not even about classes. I'm sorry that I long ago coined the
term "objects" for this topic because it gets many people to focus on the
lesser idea.

The big idea is "messaging" -- that is what the kernal of Smalltalk/Squeak
is all about (and it's something that was never quite completed in our
Xerox PARC phase). The Japanese have a small word -- ma -- for "that which
is in between" -- perhaps the nearest English equivalent is "interstitial".
The key in making great and growable systems is much more to design how its
modules communicate rather than what their internal properties and
behaviors should be. Think of the internet -- to live, it (a) has to allow
many different kinds of ideas and realizations that are beyond any single
standard and (b) to allow varying degrees of safe interoperability between
these ideas.

If you focus on just messaging -- and realize that a good metasystem can
late bind the various 2nd level architectures used in objects -- then much
of the language-, UI-, and OS based discussions on this thread are really
quite moot. This was why I complained at the last OOPSLA that -- whereas at
PARC we changed Smalltalk constantly, treating it always as a work in
progress -- when ST hit the larger world, it was pretty much taken as
"something just to be learned", as though it were Pascal or Algol.
Smalltalk-80 never really was mutated into the next better versions of OOP.
Given the current low state of programming in general, I think this is a
real mistake.

I think I recall also pointing out that it is vitally important not just to
have a complete metasystem, but to have fences that help guard the crossing
of metaboundaries. One of the simplest of these was one of the motivations
for my original excursions in the late sixties: the realization that
assignments are a metalevel change from functions, and therefore should not
be dealt with at the same level -- this was one of the motivations to
encapsulate these kinds of state changes, and not let them be done willy
nilly. I would say that a system that allowed other metathings to be done
in the ordinary course of programming (like changing what inheritance
means, or what is an instance) is a bad design. (I believe that systems
should allow these things, but the design should be such that there are
clear fences that have to be crossed when serious extensions are made.)

I would suggest that more progress could be made if the smart and talented
Squeak list would think more about what the next step in metaprogramming
should be -- how can we get great power, parsimony, AND security of meaning?

Cheers to all,


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