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␈↓ ↓H␈↓␈↓βS␈↓∧ Artificial Intelligence Laboratory, STANFORD UNIVERSITY, Stanford, California 94305

␈↓ ↓H␈↓∧Telephone 415 497-4430␈↓ 	SNovember 22, 1978 




␈↓ ↓H␈↓Professor Gerald L. Wilson
␈↓ ↓H␈↓Department of Electrical Engineering and Computer Science
␈↓ ↓H␈↓M.I.T.
␈↓ ↓H␈↓Cambridge, MA 02139

␈↓ ↓H␈↓Dear Professor Wilson:

␈↓ ↓H␈↓        Marvin␈αMinsky␈αtells␈αme␈αthat␈αI␈αhave␈αa␈αreputation␈αfor␈αlaconic␈αletters␈αof␈αreference,␈αand␈αhere's
␈↓ ↓H␈↓another.

␈↓ ↓H␈↓        I␈α≡think␈α≥the␈α≡basic␈α≡ideas␈α≥of␈α≡Hewitt's␈α≡PLANNER,␈α≥especially␈α≡as␈α≡implemented␈α≥in
␈↓ ↓H␈↓MICROPLANNER,␈α∞are␈α
a␈α∞major␈α
contribution␈α∞to␈α
computer␈α∞science.␈α
 I␈α∞think␈α
they␈α∞have␈α∞not␈α
been
␈↓ ↓H␈↓superseded␈α
by␈α
later␈α
decorations␈α
-␈α
whether␈α
by␈α
Hewitt␈α
or␈α
by␈α
others.␈α
 Hewitt's␈α
weakness,␈α
shared␈αby
␈↓ ↓H␈↓the␈α⊃other␈α⊃improvers␈α⊃of␈α⊃MICROPLANNER,␈α⊃seems␈α⊃to␈α⊃be␈α⊃that␈α⊃he␈α⊃doesn't␈α⊃know␈α⊃when␈α⊃to␈α⊂stop
␈↓ ↓H␈↓improving and start simplifying.

␈↓ ↓H␈↓        Hewitt's␈αsecond␈αmajor␈αcontribution␈αis␈αthe␈αidea␈αof␈αactors␈αand␈αits␈αassociated␈αidea␈αof␈α
regarding
␈↓ ↓H␈↓computation␈αas␈αmessage␈αpassing.␈α
 This␈αidea␈αseems␈αvery␈α
promising␈αto␈αme,␈αbut␈α
I␈αhave␈αnot␈αbeen␈α
able
␈↓ ↓H␈↓to␈αpenetrate␈α
Hewitt's␈αor␈αother␈α
people's␈αpresentations␈α
of␈αit.␈α Because␈α
much␈αinteraction␈α
of␈αprocesses
␈↓ ↓H␈↓has␈αthe␈αquality␈αof␈α
message␈αpassing,␈αit␈αseems␈α
certain␈αto␈αme␈αthat␈α
actors␈αwill␈αplay␈αan␈α
important␈αrole
␈↓ ↓H␈↓once␈αa␈αgood␈αenough␈αformalism␈αhas␈αbeen␈αdevised.␈α
 Of␈αcourse,␈αHewitt␈αis␈αnot␈αthe␈αonly␈αperson␈α
trying,
␈↓ ↓H␈↓but he certainly has a head start and has the most accomplishments to his credit.

␈↓ ↓H␈↓        As␈α
an␈α
idea␈α∞generator␈α
in␈α
computer␈α
science,␈α∞Hewitt␈α
has␈α
a␈α
high␈α∞standing.␈α
 There␈α
he␈α
is␈α∞on␈α
a
␈↓ ↓H␈↓level␈α
with␈α
Burstall␈α
and␈α∞Landin.␈α
 Elaborating␈α
his␈α
ideas␈α∞and␈α
making␈α
them␈α
practical␈α∞have␈α
become
␈↓ ↓H␈↓minor␈α→industries.␈α→ As␈α~a␈α→problem␈α→solver␈α~he␈α→has␈α→a␈α~lower␈α→standing,␈α→but␈α~still␈α→substantial
␈↓ ↓H␈↓accomplishments.␈α
 I␈αdon't␈α
remember␈α
who␈αhis␈α
graduate␈αstudents␈α
were␈α
except␈αfor␈α
Irene␈α
Greif,␈αwho
␈↓ ↓H␈↓has␈αan␈αexcellent␈αreputation.␈α There␈αis␈αevery␈αreason␈αto␈αbelieve␈αthat␈αhe␈αwill␈αcontinue␈αas␈αa␈α≡rst␈αclass
␈↓ ↓H␈↓idea␈α
generator␈α
and␈α
that␈α
others␈α
will␈α
continue␈α∞≡nding␈α
it␈α
worth␈α
the␈α
e≥ort␈α
required␈α
to␈α∞extract␈α
them
␈↓ ↓H␈↓from his somewhat vague presentations.

␈↓ ↓H␈↓        I cannot be more concrete, because I have spent my own time pursuing di≥erent ideas.
␈↓ ↓H␈↓αProfessor Gerald L. Wilson␈↓ ¬NNovember 22, 1978␈↓ 
nPage 2␈↓ 


␈↓ ↓H␈↓        I hope this is still of use.


␈↓ ↓H␈↓Sincerely,



␈↓ ↓H␈↓John McCarthy
␈↓ ↓H␈↓Director
␈↓ ↓H␈↓Professor of Computer Science