%A Daniel Watt
%T Final Report of the Brookline LOGO Project Part III:
Profiles of Individual Student's Work
%R AI Memo 546
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D September 1979
%P 222
%K mit aim ail
%O See Logo Memo 54
%Y unavailable

%A Glenn A. Iba
%T Learning Disjunctive Concepts from Examples
%R AI Memo 548
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D September 1979
%P 64
%K mit aim ail
%Y unavailable

%A Richard C. Waters
%T Mechanical Arm Control
%R AI Memo 549
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D October 1979
%P 21
%K mit aim ail
%K arm control, dynamic equations, coordinate transformation,
trajectory planning, LaGrange equations
%X This paper discusses three main problems associated with the control
of the motion of a mechanical arm.
%Y cost: $1.50, unavailable except as NTIS report AD-A084820

%A David A. McAllester
%T An Outlook On Truth Maintenance
%R AI Memo 551
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D August 1980
%P 47
%K mit aim ail
%K theorem proving, automated deduction, dependencies,
relevance, truth maintenance, backtracking, assumptions, likelihood
%X Truth maintenance systems have been used in several recent problem
solving systems to record justifications for deduced assertions, to
track down the assumptions which underlie contradictions when they
arise, and to incrementally modify assertional data structures when
assumptions are retracted.  A TMS algorithm is described here that is
substantially different from previous systems.
%Y cost: $2.75, also available as NTIS report AD-A093190

%A Beth C. Levin
%T Instrumental With And The Control Relation in English
%R AI Memo 552
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1979
%P 90
%K mit aim ail
%Y unavailable except as NTIS report AD-A078420

%A Richard M. Stallman
%T EMACS Manual for ITS Users
%R AI Memo 554
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1980
%P 218
%K mit aim ail
%O Revised April 1981
%Y unavailable except as NTIS report AD-A093186

%A Richard M. Stallman
%T EMACS Manual for TWENEX Users
%R AI Memo 555
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D September 1980
%P 241
%K mit aim ail
%O Revised May 1981, October 1981, March 1983
%X This manual documents the use and simple customization of the display
editor EMACS with the Twenex (officially known as "TOPS-20") operating
system.  The reader is not expected to be a programmer.  Even simple
customizations do not require programming skill, but the user who is
not interested in customizing can ignore the scattered customization
hints.  This is primarily a reference manual, but can be used as a
primer.
%Y cost: $3.50, also available as NTIS report AD-A093886

%A Richard M. Stallman
%T Phantom Stacks: If you look too hard, they aren't there
%R AI Memo 556
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D July 1980
%P 12
%K mit aim ail
%X A stack is a very efficient way of allocating and deallocating memory,
but it works only with a restricted pattern of usage.  Garbage
collection is completely flexible but comparatively costly.  The
implementation of powerful control structures naturally uses memory
which usually fits in with stack allocation but must have the
flexibility to do otherwise from time to time.  How can we manage
memory which only once in a while violates stack restrictions, without
paying a price the rest of the time?  This paper provides an extremely
simple way of doing so, in which only the part of the system which
actually uses the stack needs to know anything about the stack.  We
call them Phantom Stacks because they are liable to vanish if
subjected to close scrutiny.  Phantom Stacks will be used in the next
version of the Artificial Intelligence Lab's Scheme microprocessor
chip.
%Y cost: $1.50, also available as NTIS report AD-A093189

%A Francis H.C. Crick
%A David C. Marr
%A Tomaso Poggio
%T An Information Processing Approach To Understanding The Visual Cortex
%R AI Memo 557
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1980
%P 38
%K mit aim ail
%Y unavailable

%A David C. Marr
%A Tomaso Poggio
%T Some Comments on a Recent Theory of Stereopsis
%R AI Memo 558
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D July 1980
%P 8
%K mit aim ail
%Y unavailable

%A Jack Holloway
%A Guy Lewis Steele\ Jr.
%A Gerald Jay Sussman
%A Alan Bell
%T The SCHEME-79 Chip
%R AI Memo 559
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D January 1980
%P 48
%K mit aim ail
%X We have designed and implemented a single-chip microcomputer (which we
call SCHEME-79) which directly interprets a typed-pointer variant of
SCHEME, a dialect of the langugae LISP.  To support this interpreter
the chip implements an automatic storage allocation system for
heap-allocated data and an interrupt facility for user interrupt
routines implemented in SCHEME.  We describe how the machine
architecture is tailored to support the language, and the design
methodology by which the hardware was synthesized.  We develop an
interpreter for SCHEME written in LISP which may be viewed as a
microcode specification.  This is converted by successive compilation
passes into actual hardware structures on the chip.  We develop a
language embedded in LISP for describing layout artwork so we can
procedurally define generators for generalized macro components.  The
generators accept parameters to produce the specialized instances used
in a particular design.  We discuss the performance of the current
design and directions for improvement, both in the circuit performance
and in the algorithms implemented by the chip.  A complete, annotated
listing of the microcode embodied by the chip is included.
%Y cost: $2.75

%A William A. Kornfeld
%T Using Parallel Processing for Problem Solving
%R AI Memo 561
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D December 1979
%P 47
%K mit aim ail
%K parallel processing, distributed computing,
pattern-directed invocation, problem solving
%X Parallel processing as a conceptual aid in the design of programs for
problem solving applications is developed.  A pattern-directed
invocation language known as Ether is introduced.  Ether embodies two
notions in language design: activities and viewpoints.  Activities are
the basic parallel processing primitive.  Different goals of the
system can be pursued in parallel by placing them in separate
activities.  Language primitives are provided for manipulating running
activities.  Viewpoints are a generalization of context mechanisms and
serve as a device for representing multiple world models.  A number of
problem solving schemes are developed making use of viewpoints and
activities.
%Y cost: $2.75, also available as NTIS report AD-A084683

%A Lucia M. Vaina
%T Towards a Computational Theory of Semantic Memory
%R AI Memo 564
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D February 1980
%P 30
%K mit aim ail
%Y unavailable

%A W.E.L. Grimson
%T A Computer Implementation of A Theory of Human Stereo Vision
%R AI Memo 565
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D January 1980
%P 60
%K mit aim ail
%Y cost: $2.75, unavailable except as NTIS report AD-A084696

%A Katsushi Ikeuchi
%T Numerical Shape from Shading and Occluding Contours in a Single View
%R AI Memo 566
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1979
%K mit aim ail
%O Revised February 1980. See ``Artificial Intelligence'',
vol. 17, pp. 141-184, 1981
%Y unavailable as AI Memo

%A Katsushi Ikeuchi
%T Shape from Regular Patterns: An Example of Constraint Propagation in Vision
%R AI Memo 567
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D March 1980
%P 39
%K mit aim ail
%K spherical projection, propagation of constraints,
Gauss-Seidel method, texture gradient, Gaussian sphere, texture stereo
%O See Proceedings of ICPR.-80, Miami Beach, Dec. 1980, pp. l032-1039
%X An algorithm is proposed for obtaining local surface orientation from
the apparent distortion of surface patterns in an image.  A spherical
projection is used for imaging.  A mapping is defined from points on
this image sphere to a locus of points on the Gaussian sphere which
corresponds to possible surface orientations.  This mapping is based
on the measurement of the local distortions of a repeated known
texture pattern due to the imaging projection.  This locus of possible
surface orientations can be reduced to a unique orientation at each
point on the sphere using 3 vantage points and taking the intersection
of the loci of possible orientations derived from each vantage.  It is
also possible to derive a unique surface orientation at each image
point through the use of an iterative constraint propagation technique
along with the orientation information available at occluding
boundaries.  Both methods are demonstrated for real images.
%Y cost: $2.25

%A Jon Doyle
%A Philip London
%T A Selected Descriptor-Indexed Bibliography to the Literature
on Belief Revision
%R AI Memo 568
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D February 1980
%P 44
%K mit aim ail
%K artificial intelligence, bibliography, frame problem,
belief revision, logic, philosophy
%Y unavailable except as NTIS report AD-A084821

%A Henry Lieberman
%A Carl Hewitt
%T A Real Time Garbage Collector Based on the Lifetime of Objects
%R AI Memo 569A
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1980
%P 38
%K mit aim ail
%K garbage collection, temporary storage, compacting storage,
reference counting, LISP, object-oriented programming, stacks,
virtual memory
%X In previous heap storage systems, the cost of creating objects and
garbage collection is independent of the lifetime of the object
Since temporary objects account for a large portion of storage use,
it's worth optimizing a garbage collector to reclaim temporary storage
faster.  We present a garbage collection algorithm which: Makes short
term storage cheaper than long term storage, operates in real time -
object creation and access times are bounded, works well with multiple
processors and a large address space.
%Y cost: $2.25, also available as NTIS report AD-A084819

%A Sylvia Weir
%T The Evaluation and Cultivation of Spatial and Linguistic Abilities
In Individuals With Cerebral Palsy
%R AI Memo 570
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D October 1979
%P 42
%K mit aim ail
%K cerebral palsy, computer-based education, cognitive
development, computer-based diagnostics
%O See Logo Memo 55
%Y unavailable as AI Memo

%A Berthold K.P. Horn
%A Brian G. Schunck
%T Determining Optical Flow
%R AI Memo 572
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1980
%P 28
%K mit aim ail
%K optical flow, motion perception, cooperative computation,
intrinsic images, image sequences
%O See ``Artificial Intelligence'', Vol. 17, pp. 185-203, 1981
%Y unavailable except as NTIS report AD-A093925

%A J. Richter
%A S. Ullman
%T A Model For The Spatio-Temporal Organization of X- And Y-Type
Ganglion Cells In The Primate Retina
%R AI Memo 573A
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1980
%P 65
%K mit aim ail
%K retina, vision, x and y cells, motion perception
%O Revised October 1981
%X A model is proposed for the spatial and temporal characteristics of X-
and Y-type responses of ganglion cells in the primate retina.  The
model is related to a theory of directional selectivity proposed by
Marr & Ullman [1980].  The X- and Y-type responses predicted by the
model to a variety of stimuli are examined and compared with
electrophysiological recordings.  A number of implications and
predictions are discussed.
%Y cost: $3.00

%A S. Ullman
%T Against Direct Perception
%R AI Memo 574
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D March 1980
%P 44
%K mit aim ail
%X Central to contempory cognitive science is the notion that mental
processes involve computations defined over internal representations.
This notion stands in sharp contrast with another prevailing view --
the direct theory of perception, whose most prominent proponent has
been J.J. Gibson.  In this paper the notion of direct perception is
examined primarily from a theoretical standpoint, and various
objections are raised against it.  An attempt is made to place the
theory of direct perception in perspective by embedding it in a more
comprehensive framework.
%Y cost: $2.75

%A R.W. Lawler
%T One Child's Learning: Introducing Writing With A Computer
%R AI Memo 575
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D March 1980
%P 19
%K mit aim ail
%O See Logo memo 56
%Y unavailable as AI Memo

%A Randall Davis
%T Meta-Rules: Reasoning About Control
%R AI Memo 576
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D March 1980
%P 58
%K mit aim ail
%K meta-level knowledge, knowledge-based systems, strategy,
invocation, content reference, problem solving
%O See ``Artificial Intelligence'', vol. 15, 1980, pp. 179-222,
%X How can we insure that knowledge embedded in a program is applied
effectively?  Traditionally the answer to this question has been
sought in different problem solving paradigms and in different
approaches to encoding and indexing knowledge.  Each of these is
useful with a certain variety of problem, but they all share a common
problem: they become ineffective in the face of a sufficiently large
knowledge base.
%Y cost: $2.75, also available as NTIS report AD-A084639

%A Henry Lieberman
%A Carl Hewitt
%T A Session With TINKER: Interleaving Program Testing With Program Design
%R AI Memo 577
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1980
%P 37
%K mit aim ail
%O See Proceedings of LISP Conference, Stanford, August 1980. pp. 90-99
%X Tinker is an experimental interactive programming system which
integrates program testing with program design.  New procedures are
created by working out the steps of the procedure in concrete
situations.  Tinker displays the results of each step as it is
performed, and constructs a procedure for the general case from sample
calculations.  The user communicates with Tinker mostly by selecting
operations from menus on an interactive graphic display rather than by
typing commands.  This paper presents a demonstration of our current
implementation of Tinker.
%Y cost: $2.25, also available as NTIS report AD-A095521

%A K.F. Prazdny
%A Mike Brady
%T Extra-Retinal Signals Influence Induced Motion: A New Kinetic Illusion
%R AI Memo 580
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1980
%P 33
%K mit aim ail
%K induced motion, eye movements, tracking
%Y unavailable except as NTIS report AD-A093191

%A Judi Jones
%T Primer for R users
%R AI Memo 585
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D September 1980
%P 15
%K mit aim ail
%Y unavailable

%A Robert W. Lawler
%T The Progressive Construction of Mind
%R AI Memo 586
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1980
%P 60
%K mit aim ail
%K learning, cognitive psychology, genetic epistemology,
artificial intelligence, cognitive science, mental models,
computers and education, arithmetic
%O See Logo memo 57, also published in ``Cognitive Science'',
Vol. 5, January 1981, pp. 1-30
%Y unavailable as AI Memo

%A Guy L. Steele\ Jr.
%T Destructive Reordering of CDR-Coded Lists
%R AI Memo 587
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D August 1980
%P 15
%K mit aim ail
%K list structure, linked lists, CDR-coding, LISP, data structures,
sorting, merge sorting, destructive list operations
%X Linked list structures can be compactly represented by encoding the
CDR ("next") pointer in a two-bit field and linearizing list
structures as much as possible.  This "CDR-coding" technique can save
up to 50% on storage for linked lists.  We present here algorithms
for destructive reversal and sorting of CDR-coded lists which avoid
creation of indirect pointers.  The essential idea is to note that a
general list can be viewed as a linked list of array-like "chunks".
The algorithm applied to such "chunky lists" is a fusion of
separate-array and list-specific algorithms; intuitively, the
array-specific algorithm is applied to each chunk, and the list
algorithm to the list with each chunk considered as a single element.
%Y cost: $1.50

%A Robert W. Lawler
%T Extending A Powerful Idea
%R AI Memo 590
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D July 1980
%P 21
%K mit aim ail
%K computers and education, mathematics education, computer
designs, cognitive psychology
%O See Logo memo 58
%Y unavailable as AI Memo

%A Shimon Ullman
%T Interfacing The One-Dimensional Scanning of an Image With
The Applications of Two-Dimensional Operators
%R AI Memo 591
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1980
%P 13
%K mit aim ail
%K image processing, convolution, scanning
%Y unavailable except as NTIS report AD-A093932

%A D.D. Hoffman
%T Inferring Shape From Motion Fields
%R AI Memo 592
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D December 1980
%P 19
%K mit aim ail
%K velocity field, surface normal
%Y unavailable except as NTIS report AD-A099150

%A Mike Brady
%T Toward A Computational Theory of Early Visual Processing In Reading
%R AI Memo 593
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D September 1980
%P 42
%K mit aim ail
%X This paper is the first of a series aimed at developing a theory of
early visual processing in reading.  We suggest that there has been a
close parallel in the development of theories of reading and theories
of vision in Artificial Intelligence.  We propose to exploit and
extend recent results in computer Vision to develop an improved model
of early processing in reading.  This first paper considers the
problem of isolating words in text based on the information which Marr
and Hildreth's (1980) theory asserts is available in the parafovea.
%Y cost: $2.75, also available as NTIS report AD-A093185

%A Koji Fukumori
%T Fundamental Scheme For Train Scheduling
%R AI Memo 596
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D September 1980
%P 24
%K mit aim ail
%K time scheduling, railroad, train time-tables, search,
propagation of constraints
%Y unavailable

%A David Marr
%A Lucia Vaina
%T Representation and Recognition of the Movement of Shapes
%R AI Memo 597
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D October 1980
%P 25
%K mit aim ail
%K 3-D model representation, movements, shape
%X The problems posed by the representation and recognition of the
movements of 3-D shapes are analyzed.  A representation is proposed
for the movements of shapes that lie within the scope of Marr &
Nishihara's (1978) 3-D model representation of static shapes.  The
basic problem is, how to segment a stream of movement into pieces each
of which can be described separately.  The representation proposed
here is based upon segmenting a movement at moments when a component
axis, e.g. an arm starts to move relative to its local coordinate
frame (here, the torso). So that for example walking is divided into a
sequence of the stationary states between each swing of the arms and
legs, and the actual motions between the stationary points (relative
to the torso, not the ground).
%Y cost: $2.75, also available as NTIS report AD-A097853

%A John Batali
%A Anne Hartheimer
%T The Design Procedure Language Manual
%R AI Memo 598
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D September 1980
%P 81
%K mit aim ail
%K integrated circuits, VLSI, computer aided design, data bases
%O See VLSI Memo 80-31
%X This manual describes the Design Procedure language (DPL) for LSI
design.  DPL creates and maintains a representation of a design in a
hierarchically organized, object-oriented LISP data-base.  Designing
in DPL involves writing programs (Design Procedures) which construct
and manipulate descriptions of a project.  The programs use a
call-by-keyword syntax and may be entered interactively or written by
other programs.  DPL is the layout language for the LISP based
Integrated Circuit design system (LISPIC) being developed at the
Artificial Intelligence Laboratory at MIT.  The LISPIC design
environment will combine a large set of design tools that interact
through a common data-base.
%Y cost: $3.00, also available as NTIS report AD-A093933

%A Boris Katz
%T A Three-Step Procedure For Language Generation
%R AI Memo 599
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D December 1980
%P 40
%K mit aim ail
%K language generation, parsing, transformations, natural language
%X This paper outlines a three-step plan for generating English text from
any semantic representation by applying a set of syntactic
transformations to a collection of kernel sentences.  The paper
focuses on describing a program which realizes the third step of this
plan. Step One separates the given representation into groups and
generates from each group a set of kernel sentences.  Step Two must
decide, based upon both syntactic and thematic considerations, the set
of transformations that should be performed upon each set of kernels.
The output of the first two steps provides the "TASK" for Step Three.
Each element of the TASK corresponds to the generation of one English
sentence, and in turn may be defined as a triple consisting of: (a) a
list of kernel phrase markers; (b) a list of transformations to be
performed upon the list of kernels; (c) a "syntactic separator" to
separate or connect generated sentences.  Step Three takes as input
the results of Step One and Step Two.  The program which implements
Step Three "reads" the TASK, executes the transformations indicated
there, combines the altered kernels of each set into a sentence,
performs a pronominalization process, and finally produces the
appropriate English word string.  This approach subdivides a hard
problem into three more manageable and relatively independent pieces.
It uses linguistically motivated theories at Step Two and Step Three.
As implemented so far, Step Three is small and highly efficient.  The
system is flexible; all the transformations can be applied in any
order.  The system is general; it can be adapted easily to many
domains.
%Y $2.75, also available as NTIS report AD-A131537

%A James L. Stansfield
%T Conclusions From The Commodity Expert Project
%R AI Memo 601
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1980
%P 36
%K mit aim ail
%K intelligent assistant, knowledge representation,
qualitative reasoning, commodities
%X The goal of the commodity expert project was to develop a prototype
program that would act as an intelligent assistant to a commodity
market analyst.  Since expert analysts must deal with very large, yet
incomplete, data bases of unreliable facts about a complex world, the
project would stringently test the applicability of Artificial
Intelligence techniques.  After a significant effort however, I am
forced to the conclusion that an intelligent, real-world system of the
kind envisioned is currently out of reach.  Some of the difficulties
were due to the size and complexity of the domain.  As its true scale
became evident, the available resources progressively appeared less
adequate.  The representation and reasoning problems that arose were
persistently difficult and fundamental work is needed before the tools
will be sufficient to engineer truly intelligent assistants.  Despite
these difficulties, perhaps even because of them, much can be learned
from the project.  To assist future applications projects, I explain
in this report some of the reasons for the negative result, and also
describe some positive ideas that were gained along the way.  In doing
so, I hope to convey the respect I have developed for the complexity
of real-world domains, and the difficulty of describing the ways
experts deal with them.
%Y cost: $2.25, also available as NTIS report AD-A097854

%A Daniel Weinreb
%A David Moon
%T Flavors: Message Passing in the Lisp Machine
%R AI Memo 602
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1980
%P 35
%K mit aim ail
%K flavor, message passing, actors, smalltalk, generic functions
%X The object oriented programming style used in the Smalltalk and Actor
languages is available in Lisp Machine Lisp, and used by Lisp Machine
software system. It is used to perform generic operations on objects.
Part of its implementation is simply a convention in procedure calling
style; part is a powerful language feature, called Flavors, for
defining abstract objects.  This chapter attempts to explain what
programming with objects and with message passing means, the various
means of implementing these in Lisp Machine Lisp, and when you should
use them.  It assumes no prior knowledge of any other languages.
%Y cost: $2.25, also available as NTIS report AD-A095523

%A Marvin Minsky
%T Jokes and the Logic of the Cognitive Unconscious
%R AI Memo 603
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1980
%P 25
%K mit aim ail
%K memory, knowledge, bugs, frame, logic
%X Freud's theory of jokes explains how they overcome the mental
"censors" that make it hard for us to think "forbidden" thoughts.  But
his theory did not work so well for humorous nonsense as for other
comical subjects.  In this essay I argue that the different forms of
humor can be seen as much more similar, once we recognize the
importance of Knowledge about knowledge and, particularly, aspects of
thinking concerned with recognizing and suppressing bugs--ineffective
or destructive thought processes.  When seen in this light, much humor
that at first seems pointless, or mysterious, becomes more
understandable.
%Y cost: $2.25

%A Tomas Lozano-Perez
%T Spatial Planning: A Configuration Space Approach
%R AI Memo 605
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D December 1980
%P 37
%K mit aim ail
%K geometric algorithms, collision avoidance, robotics
%X This paper presents algorithms for computing constraints on the
position of an object due to the presence of obstacles.  This problem
arises in applications which require choosing how to arrange or move
objects among other objects.  The basis of the approach presented here
is to characterize the position and orientation of the object of
interest as a single point in a Configuration Space, in which each
coordinate represents a degree of freedom in the position and/or
orientation of the object.  The configurations forbidden to this
object, due to the presence of obstacles, can then be characterized as
regions in the Configuration Space.
%Y cost: $2.25, also available as NTIS report AD-A093934

%A Tomas Lozano-Perez
%T Automatic Planning of Manipulator Transfer Movements
%R AI Memo 606
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D December 1980
%P 54
%K mit aim ail
%K robotics, collision avoidance, path planning, grasping
%Y unavailable except as NTIS report AD-A096118

%A D.D. Hoffman
%A B.E. Flinchbaugh
%T The Interpretation of Biological Motion
%R AI Memo 608
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D December 1980
%P 22
%K mit aim ail
%K biological motion, planarity assumption
%Y unavailable

%A Barbara S. Kerns
%T Towards A Better Definition of Transactions
%R AI Memo 609
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D December 1980
%P 13
%K mit aim ail
%K transactions, data bases, actors, interactive systems
%Y unavailable except as NTIS report AD-A093935

%A Richard C. Waters
%T GPRINT - A LISP Pretty Printer Providing Extensive
User Format-Control Mechanisms
%R AI Memo 611A
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D October 1981
%P 29
%K mit aim ail
%K pretty printing, formatted output, programming environments, LISP
%O revised September 1982,
See ACM Transactions on Programming Languages and
Systems,  Vol. 5, No. 4, October 1983, pp. 513-531.
%X A Lisp pretty printer is presented which makes it easy for a user to
control the format of the output produced.  The printer can be used as
a general mechanism for printing data structures as well as programs.
It is divided into two parts: a set of formatting functions, and an
output routine.  The user specifies how a particular type of object
should be formatted by creating a formatting function for the type.
When passed an object of that type, the formatting function creates a
sequence of directions which specify how the object should be printed
if it can fit on one line and how it should be printed if it must be
broken up across multiple lines.  A simple template language makes it
easy to specify these directions.  Based on the line length availabe,
the output routine decides what structures have to be broken up across
multiple lines and produces the actual output following the directions
created by the formatting functions.  The paper concludes with a
discussion of how the pretty printing method presented could be
applied to languages other than Lisp.
%Y cost: $2.25, also available as NTIS report AD-A124261

%A B.K.P. Horn
%T The Curve of Least Energy
%R AI Memo 612A
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D January 1981
%P 34
%K mit aim ail
%K spline, subjective contours, smooth curve, computer aided design
%X Here we search for the curve which has the smallest integral of the
square of curvature, while passing through two given points with given
orientation.  This is the true shape of a spline used in lofting.  In
computer-aided design, curves have been sought which maximize
"smoothness".  The curve discussed here is the one arising in this way
from a commonly used measure of smoothness.  The human visual system
may use such a curve when it constructs a subjective contour.
%Y cost: $2.25, also available as NTIS report AD-A098054

%A W.E.L. Grimson
%T A Computational Theory of Visual Surface Interpolation
%R AI Memo 613
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1981
%P 75
%K mit aim ail
%K stereo vision, surface interpolation, natural computation,
quadratic variation
%X Computational theories of structure from motion and stereo vision only
specify the computation of three-dimensional surface information at
special points in the image.  Yet, the visual perception is clearly of
complete surfaces.  In order to account for this, a computational
theory of the interpolation of surfaces from visual information is
presented.  The problem is constrained by the fact that the surface
must agree with the information from stereo or motion correspondence,
and not vary radically between these points.  Using the image
irradiance equation [Horn, 1977], an explicit form of this surface
consistency constraint can be derived [Grimson, 1981c].
%Y cost: $3.00, also available as NTIS report AD-A103921

%A W.A. Richards
%A J.M. Rubin
%A D.D. Hoffman
%T Equation Counting and the Interpretation of Sensory Data
%R AI Memo 614
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1981
%P 26
%K mit aim ail
%K vision, color-vision, structure from motion, perception,
equation-counting, motion, signal detection, inference
%Y unavailable except as NTIS report AD-A103924

%A Marvin Minsky
%T Music, Mind, and Meaning
%R AI Memo 616
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D February 1981
%P 21
%K mit aim ail
%K cognition, music, semantics, representation of knowledge
%X Speculating about cognitive aspects of listening to music, this essay
discusses: how metric regularity and thematic repetition might involve
representation frames and memory structures, how the result of
listening might resemble space-models, how phrasing and expression
might evoke innate responses and, finally, why we like music -- or
rather, what is the nature of liking itself.
%Y cost: $2.25

%A Kok Huang Lim
%T Control of a Tendon Arm
%R AI Memo 617
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D February 1981
%P 85
%K mit aim ail
%K robotics, tendon actuation, time optimal control
%X The dynamics and control of a tendon driven three degree of freedom
shoulder joint are studied.  A control scheme consisting of two phases
has been developed.  In the first phase, approximation of the time
optimal control trajectory was applied open loop to the system.  In
the second phase a closed loop linear feedback law was employed to
bring the system to the desired final state and to maintain it there.
%Y cost: $3.00, available as NTIS report AD-A098089

%A Gerald R. Barber
%T Record of the Workshop on Research in Office Semantics
%R AI Memo 620
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D February 1981
%P 18
%K mit aim ail
%K office automation, knowledge-based office systems
%X This paper is a compendium of the ideas and issues presented at the
Chatham Bars Workshop on Office Semantics.  The intent of the workshop
was to examine the state of the art in office systems and to elucidate
the issues system designers were concerned with in developing next
generation office systems.  The workshop involved a cross-section of
people from government, industry and academia.  Presentations in the
form of talks and video tapes were made of prototypical systems.
%Y cost: $1.50

%A William M. Silver
%T On the Representation of Angular Velocity and its Effect on the Efficien
cy of Manipulator Dynamics Computation}
%R AI Memo 622
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D March 1981
%P 28
%K mit aim ail
%K robotics, Lagrangian dynamics, manipulators, Newton-Euler dynamics
%X Recently there has been considerable interest in efficient
formulations of manipulator dynamics, mostly due to the desirability
of real-time control or analysis of physical devices using modest
computers.  The inefficiency of the classical Lagrangian formulation
is well known, and this has led researchers to seek alternative
methods.  Several authors have developed a highly efficient
formulation of manipulator dynamics based on the Newton-Euler
equations, and there may be some confusion as to the source of this
efficiency.  This paper shows that there is in fact no fundamental
difference in computational efficiency between Lagrangian and
Newton-Euler equations, and there may be some confusion as to the
source of this efficiency.  This paper shows that there is in fact no
fundamental difference in computational efficiency between Lagrangian
and Newton-Euler formulations.  The efficiency of the above-mentioned
Newton-Euler formulation is due to two factors: the recursive
structure of the computation and the representation chosen for the
rotational dynamics.  Both of these factors can be achieved in the
Lagrangian formulation, resulting in an algorithm identical to the
Newton-Euler formulation.  Recursive Lagrangian dynamics has been
discussed previously by Hollerbach.  This paper takes the final step
by comparing in detail the representations that Lagrangian formulation
is indeed equivalent to the Newton-Euler formulation.
%Y cost: $2.25, also available as NTIS report AD-A098418

%A Randall Davis
%A Reid G. Smith
%T Negotiation as a Metaphor for Distributed Problem Solving
%R AI Memo 624
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1981
%P 43
%K mit aim ail
%K distributed problem solving, contract net, loosely coupled systems
%O See ``Artificial Intelligence'', Vol. 20, 1983, pgs. 63-109.
%X We describe the concept of distributed problem solving and define it
as the cooperative solution of problems by a decentralized and loosely
coupled collection of problem solvers.  This approach to problem
solving offers the promise of increased performance and provides a
useful medium for exploring and developing new problem-solving
techniques.  We present a framework called the contract net that
specifies communication and control in a distributed problem solver.
Task distribution is viewed as an interactive process, a discussion
carried on between a node with a task to be executed and a group of
nodes that may be able to execute the task.  We describe the kinds of
information that must be passed between nodes during the discussion in
order to obtain effective problem-solving behavior.  This discussion
is the origin of the negotiation metaphor: Task distribution is viewed
as a form of contract negotiation.
%Y cost: $2.75, also available as NTIS report AD-A100367

%A Henry Lieberman
%T A Preview of Act 1
%R AI Memo 625
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1981
%P 30
%K mit aim ail
%K actors, object-oriented programming, message passing,
knowledge representation, data abstraction, parallelism
%X The next generation of artificial intelligence programs will require
the ability to organize knowledge as groups of active objects.  Each
object should have only its own local expertise, the ability to
operate in parallel with other objects, and the ability to communicate
with other objects.  Artificial Intelligence programs will also
require a great deal of flexibility, including the ability to support
multiple representations of objects, and to incrementally and
transparently replace objects with new, upward-compatible versions.
To realize this, we propose a model of computation based on the notion
of an actor, an active object that communicates by message passing.
Actors blur the conventional distinction between data and procedures.
The actor philosophy is illustrated by a description of our prototype
actor interpreter Act 1.
%Y cost: $2.25

%A Henry Lieberman
%T Thinking About Lots Of Things At Once Without Getting Confused -
Parallelism in Act 1
%R AI Memo 626
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1981
%P 23
%K mit aim ail
%K actors, parallelism, futures, serializers, data abstraction,
synchronization, message passing
%X As advances in computer architecture and changing economics make
feasible machines with large-scale parallelism, Artificial
Intelligence will require new ways of thinking about computation that
can exploit parallelism effectively.  We present the actor model of
computation as being appropriate for parallel systems, since it
organizes knowledge as active objects acting independently, and
communicating by message passing.  We describe the parallel constructs
in our experimental actor interpreter Act 1. Futures create
concurrency, by dynamically allocating processing resources much as
Lisp dynamically allocates passive storage.  Serializers restrict
concurrency by constraining the order in which events take place, and
have changeable local state.  Using the actor model allows parallelism
and synchronization to be implemented transparently, so that parallel
or synchronized resources can be used as easily as their serial
counterparts.
%Y cost: $2.25

%A William A. Kornfeld
%T The Use of Parallelism to Implement a Heuristic Search
%R AI Memo 627
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D March 1981
%P 17
%K mit aim ail
%K constraint networks, parallelism, search strategies,
problem solving
%X The role of parallel processing in heuristic search is examined by
means of an example (cryptarithmetic addition).  A problem solver is
constructed that combines the metaphors of constraint propagation and
hypothesize-and-test.  The system is capable of working on many
incompatible hypotheses at one time.  Furthermore, it is capable of
allocating different amounts of processing power to running activities
and changing these allocations as computation proceeds.  It is
empirically found that the parallel algorithm is on the average, more
efficient than a corresponding sequential one.  Implications of this
for problem solving in general are discussed.
%Y cost: $1.50, also available as NTIS report AD-A099184

%A David A. Moon
%T Chaosnet
%R AI Memo 628
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1981
%P 62
%K mit aim ail
%K local network, system
%X Chaosnet is a local network, that is, a system for communication among
a group of computers located within about 1000 meters of each other.
Originally developed by the Artificial Intelligence Laboratory as the
internal communications medium of the Lisp Machine System, it has
since come to be used to link a variety of machines around MIT and
elsewhere.
%Y cost: $2.75, also available as NTIS report AD-A104024

%A William Daniel Hillis
%T Active Touch Sensing
%R AI Memo 629
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1981
%P 36
%K mit aim ail
%K touch, tactile sensor, tendon, robots, finger
%X The mechanical hand of the future will roll a screw between its
fingers and sense, by touch, which end is which.  This paper describes
a step toward such a manipulator--a robot finger that is used to
recognize small objects by touch.  The device incorporates a novel
imaging tacticle sensor--an artificial skin with hundreds of pressure
sensors in a space the size of a finger tip.  The sensor is mounted on
a tendon-actuated mechanical finger, similar in size and range of
motion to a human index finger.  A program controls the finger, using
it to press and probe the object placed in front of it.  Based on how
the object feels, the program guesses its shape and orientation and
then uses the finger to test refine the hypothesis.  The device is
programmed to recognize commonly used fastening devices-nuts, bolts,
flat washers, lock washers, dowel pins, cotter pins, and set screws.
%Y cost: $2.25, also available as NTIS report AD-A099255

%A John M. Rubin
%A W.A. Richards
%T Color Vision and Image Intensities: When are Changes Material?
%R AI Memo 631
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1981
%P 32
%K mit aim ail
%K vision, edge detection, crosspoint operators, color-vision,
material changes
%X Marr has emphasized the difficulty in understanding a biological
system or its components without some idea of its goals.  In this
paper, a preliminary goal for color vision is proposed and analyzed.
That goal is to determine where changes of material occur in a scene
(using only spectral information).  This goal is challenging for two
reasons.  First, the effects of many processes (shadowing, shading
from surface orientation changes, highlights, variations in pigment
density) are confounded with the effects of material changes in the
available image intensities.  Second, material changes are essentially
arbitrary.  We are consequently led to a strategy of rejecting the
presence of such confounding process.  We show that there is a unique
condition, the spectral crosspoint, that allows rejection of the
hypothesis that measured image intensities arise from one of the
confounding processes. (If plots are made of image intensity versus
wavelength from two image regions, and the plots intersect, we say
that there is a spectral crosspoint).
%Y cost: $2.25, also available as NTIS report AD-A103926

%A Patrick H. Winston
%T Learning New Principles From Precedents And Exercises: The Details
%R AI Memo 632
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1981
%P 60
%K mit aim ail
%K learning, principles, theory, analogy-based reasoning
%X Much learning is done by way of studying precedents and exercises.  A
teacher supplies a story, gives a problem, and expects a student both
to solve a problem and to discover a principle.  The student must find
the correspondence between the story and the problem, apply the
knowledge in the story to solve the problem, generalize to form a
principle, and index the principle so that it can be retrieved when
appropriate.  This sort of learning pervades Management, Political
Science, Economics, Law, and Medicine as well as the development of
common-sense knowledge about life in general.  This paper presents a
theory of how it is possible to learn by precedents and exercises and
describes an implemented system that exploits the theory.  The theory
holds that causal relations identify the regularities that can be
exploited from past experience, given a satisfactory representation
for situations.  The representation used stresses actors and objects
which are taken from English-like input and arranged into a kind of
semantic network.  Principles emerge in the form of production rules
which are expressed in the same way situations are.
%Y cost: $2.75, also available as NTIS report AD-A100368

%A Charles Rich
%A Richard Waters
%T Abstraction, Inspection And Debugging In Programming
%R AI Memo 634
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1981
%P 31
%K mit aim ail
%K artificial intelligence, Programmer's Apprentice, debugging,
plans, automatic programming, program editor, programming environments
%X We believe that software engineering has much to learn from other
mature engineering disciplines, such as electrical engineering, and
that the problem solving behaviors of engineers in different
disciplines have many similarities.  Three key ideas in current
artificial intelligence theories of engineering problem solving are:
Abstraction--using a simplified view of the problem to guide the
problem solving process.  Inspection--problem solving by recognizing
the form ("plan") of a solution.  Debugging--incremental modification
of an almost satisfactory solution to a more satisfactory one.  These
three techniques are typically used together in a paradigm which we
call AID (for Abstraction, Inspection, Debugging): First an abstract
model of the problem is constructed in which some important details
are intentionally omitted.  In this simplified view inspection methods
are more likely to succeed, yielding the initial form of a solution.
Further details of the problem are then added one at a time with
corresponding incremental modifications to the solution.  This paper
states the goals and milestones of the remaining three years of a five
year research project to study the fundamental principles underlying
the design and construction of large software systems and to
demonstrate the feasibility of a computer aided design tool for this
purpose, called the programmer's apprentice.
%Y cost: $2.25, also available as NTIS report AD-A102157

%A John M. Hollerbach
%A Tamar Flash
%T Dynamic Interactions between Limb Segments during Planar Arm Movement
%R AI Memo 635
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1981
%P 23
%K mit aim ail
%K arm movement, motor control, limb dynamics
%Y unavailable

%A Kent A. Stevens
%T Evidence Relating Subjective Contours And Interpretations Involving Occlusion
%R AI Memo 637
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1981
%P 12
%K mit aim ail
%K subjective contours, vision, occlusion, perception
%O Replaces Memo 363
%X Subjective contours, according to one theory, outline
surfaces that are apparently interposed between the viewer and
background (because of the disruption of background figures, sudden
termination of lines, and other occlusion "cues") but are not
explicitly outlined by intensity discontinuities.  This theory
predicts that if occlusion cues are not interpreted as evidence of
occlusion, no intervening surface need be postulated, hence no
subjective contours would be seen.  This prediction, however, is
difficult to test because observers normally interpret the cues as
occlusion evidence and normally see the subjective contours.  This
article describes a patient with visual agnosia who is both unable to
make the usual occlusion interpretions and is unable to see subjective
contours.  He has, however, normal abililty to interpret standard
visual illusions, stereograms, and in particular, stereogram versions
of the standard subjective contour figures, which elicit to him strong
subjective edges in depth (corresponding to the subjective contours
viewed in the monocular versions of the figures).
%Y cost: $1.50, also available as NTIS report AD-A103925

%A Daniel G. Shapiro
%T Sniffer: a System that Understands Bugs
%R AI Memo 638
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1981
%P 59
%K mit aim ail
%K debugging, error recognition, bugs, program understanding,
expert systems
%O This paper was originally submitted as master's thesis to
the MIT Dept. of Electrical Engineering and Computer Science on May 8, 1981
%X This paper presents a bug understanding system, called ``sniffer'',
which applies inspection methods to generate a deep understanding of a
narrow class of errors.  Sniffer is an interactive debugging aide.  It
can locate and identify error-containing implementations of typical
programming cliches, and it can describe them using the terminology
employed by expert programmers.  The debugging knowledge in Sniffer is
organized as a collection of independent experts which understand
specific errors.  Each expert functions by applying a feature
recognition process to the test program (the program under analysis),
and to the events which took place during the execution of that code.
No deductive machinery is involved.  This recognition is supported by
two systems; the ``cliche finder'' which identifies small portions
of algorithms from a plan for the code, and the ``time rover''
which provides access to all program states which occured during the
test program's execution.
%Y cost: $2.75, also available as NTIS report AD-A102158

%A Laurence Miller
%T Natural Learning
%R AI Memo 640
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D October 1981
%P 185
%K mit aim ail
%K learning, interactive control, equilibration,
interest, micro-worlds
%O See Logo memo 61
%X This memo reports the results of a case study into how children learn
in the absence of explicit teaching.  The three subjects, an eight
year old, a ten year old and a thirteen year old were observed in both
of two experimental micro-worlds.  The first of these micro-worlds,
called the Chemicals World, included a large table, a collection of
laboratory and household chemicals, and apparatus for conducting
experiments with chemicals; the second, called the Mork and Mindy
World included a collection of video-taped episodes of the television
series Mork and Mindy, a video-tape machine and an experimenter with
whom the subjects could discuss the episodes.  The main result of the
study is a theory of how children's interests interact with knowledge
embodied in their environment causing them to learn new powerful
ideas.  An early version of this theory is presented in chapter five.
%Y cost: $3.50

%A William A. Kornfeld
%A Carl Hewitt
%T The Scientific Community Metaphor
%R AI Memo 641
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D January 1981
%P 11
%K mit aim ail
%K parallelism, problem solving, philosophy of science
%X Scientific communities have proven to be extremely successful at
solving problems.  They are inherently parallel systems and their
macroscopic nature makes them amenable to careful study.  In this
paper the character of scientific research is examined drawing on
sources in the philosophy and history of science.  We maintain that
the success of scientific research depends critically on its
concurrency and pluralism.  A variant of the language Ether is
developed that embodies notions of concurrency necessary to emulate
some of the problem solving behavior of scientific communities.
Capabilities of scientific communities are discussed in parallel with
simplified models of these capabilities in this language.
%Y cost: $1.50, also available as NTIS report AD-A108178

%A Giuseppe Attardi
%A Maria Simi
%T Semantics of Inheritance and Attributions in the Description System Omega
%R AI Memo 642
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D August 1981
%P 38
%K mit aim ail
%K description, inheritance, semantic networks, model, attribute,
knowledge representation, logic, consistency
%X Omega is a description system for knowledge embedding which
incorporates some of the attractive modes of expression in natural
language such as descriptions, inheritance, quantification, negation,
attributions and multiple viewpoints.  Omega represents an
investigation both on logic formalisms more expressive than first
order predicate logic and on the foundations of knowledge
representation.  The logic of Omega combines mechanisms of the
predicate calculus, type systems, and set theory.  As a logic, Omega
achieves the goal of an intuitively sound and consistent theory of
classes which permits unrestricted abstraction within a powerful logic
system.  Description abstraction is the construct provided in Omega
corresponding to set abstraction.  Attributions and inheritance are
the basic mechanisms for knowledge structuring.  To achieve
flexibility and incrementality, the language allows to express
descriptions with an arbitrary number of attributions, rather than
predicates with a fixed number of arguments as in predicate logic.
This requires an unusual interpretation for instance descriptions,
which in turn provides insights into the use and meaning of several
kind of attributions.  The logic foundations for Omega are
investigated.  Semantic models are provided, and axiomatization is
derived and the consistency and completeness of the logic is
established.
%Y cost: $2.75, also available as NTIS report AD-A104776

%A Richard M. Stallman
%T A Local Front End for Remote Editing
%R AI Memo 643
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D February 1982
%P 28
%K mit aim ail
%K communications, editor, networks, display, extensible
%X The Local Editing Protocol allows a local programmable terminal to
execute the most common editing commands on behalf of an extensible
text editor on a remote system, thus greatly improving speed of
response without reducing flexibility.  The Line Saving Protocol
allows the local system to save text which is not displayed, and
display it again later when it is needed, under the control of the
remote editor.  Both protocols are substantially system and editor
independent.
%Y cost: $2.25, also available as NTIS report AD-A113496

%A Richard M. Stallman
%T The SUPDUP Protocol
%R AI Memo 644
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D July 1983
%P 42
%K mit aim ail
%K communications, display, networks
%X
The SUPDUP protocol provides for login to a remote system over a
network with terminal-independent output, so that only the local
system need know now to handle the user's terminal.  It offers
facilities for graphics and for local assistance to remote text
editors.  This memo contains a complete description of the SUPDUP
protocol in fullest possible detail.
%Y cost: $2.75

%A Tomaso Poggio
%T Marr's Approach to Vision
%R AI Memo 645
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D August 1981
%P 7
%K mit aim ail
%K Marr, computational approach, biological visual perception,
zero crossings
%X In the last seven years a new computational approach has led to
promising advances in the understanding of biological visual
perception.  The foundations of the approach are largely due to the
work of a single man, David Marr at M.I.T.  Now, after his death in
Boston on November 17th 1980, research in vision will not be the same
for the growing number of those who are following his lead.
%Y cost: $1.50, also available as NTIS report AD-A104198

%A W. Daniel Hillis
%T The Connection Machine
%R AI Memo 646
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D September 1981
%P 29
%K mit aim ail
%K concurrent architecture, content addressable memory,
multiprocessing, associative memory, parallel computers,
tessellated, cellular array
%X This paper describes the connection memory, a machine for concurrently
manipulating knowledge stored in semantic networks.  We need the
connection memory because conventional serial computers cannot move
through such networks fast enough.  The connection memory sidesteps
the problem by providing processing power proportional to the size of
the network.  Each node and link in the network has its own simple
processor.  These connect to form a uniform locally-connected network
of perhaps a million processor/memory cells.
%Y cost: $2.25, also available as NTIS report AD-A107463

%A Marvin Minsky
%T Nature Abhors an Empty Vacuum
%R AI Memo 647
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D August 1981
%P 13
%K mit aim ail
%K discrete-physics, quantum, Heisenberg, vacuum
%X Imagine a crystalline world of tiny, discrete "cells", each knowing
only what its nearest neighbors do.  Each volume of space contains
only a finite amount of information, because space and time come in
discrete units.  In such a universe, we'll construct analogs of
particles and fields -- and ask what it would mean for these to
satisfy constraints like conservation of momentum.  In each case
classical mechanics will break down -- on scales both small and large,
and strange phenomena emerge: a maximal velocity, a slowing of
internal clocks, a bound on simultaneous measurement, and quantum-like
effects in very weak, or intense fields.
%Y cost: $1.50, also available as NTIS report AD-A106362

%A W.A. Richards
%T A Lightness Scale from Image Intensity Distributions
%R AI Memo 648
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D August 1981
%P 36
%K mit aim ail
%Y unavailable except as NTIS report AD-109917

%A T. Poggio
%A C. Koch
%A V. Torre
%T Microelectronics in Nerve Cells: Dendritic Morphology and
Information Processing
%R AI Memo 650
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D October 1981
%P 52
%K mit aim ail
%K cable theory, microelectronics, ganglion cells, synapses,
motion detection
%X The electrical properties of the different anatomical types of retinal
ganglion cells in the cat were calculated on the basis of passive
cable theory from measurements made on histological material provided
by Boycott and Wassle (1974).  The interactions between excitation and
inhibition when the inhibitory battery is near the resting potential
can be strongly nonlinear in these cells.  We analyze some of the
integrative properties of an arbitrary passive dendritic tree and we
then derive the functional properties which are characteristic for the
various types of ganglion cells.  In particular, we derive several
general results concerning the spatial specificity of shunting
inhibition in "vetoing" an excitatory input (the "on path" property)
and its dependence on the geometrical and electric properties of the
dendritic tree.  Our main conclusion is that specific branching
patterns coupled with a suitable distribution of synapses are able to
support complex information processing operations on the incoming
signals.  Thus, a neuron seems likely to resemble an (analog) LSI
circuit with thousands of elementary processing
units - the synapses - rather than a single logical gate.  A dendritic
tree would then be near to the ultimate in microelectronics with
little patches of postsynaptic membrane representing the fundamental
units for several elementary computations.
%Y cost: $2.75

%A David Chapman
%T A Program Testing Assistant
%R AI Memo 651
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1981
%P 24
%K mit aim ail
%K debugging, program testing assistant, Programmer's Apprentice,
programming environment, testing
%X This paper describes the design and implementation of a program
testing assistant which aids a programmer in the definition,
execution, and modification of test cases during incremental program
development.  The testing assistant helps in the interactive
definition of test cases and executes them automatically when
appropriate.  It modifies test cases to preserve their usefulness when
the program they test undergoes certain types of design changes.  The
testing assistant acts as a fully integrated part of the programming
environment and cooperates with existing programming tools, including
a display editor, compiler, interpreter, and debugger.
%Y cost: $2.25, also available as NTIS report AD-A108147

%A Robert Lawler
%T Some Powerful Ideas
%R AI Memo 652
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D December 1981
%P 26
%K mit aim ail
%O See Logo Memo 60
%Y unavailable

%A Michael Brady
%T Computational Approaches to Image Understanding
%R AI Memo 653
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D October 1981
%P 186
%K mit aim ail
%O See ``Computing Surveys'', Vol. 14, No. 1, 15 March 1982
%X Recent theoretical developments in Image Understanding are surveyed
Among the issues discussed are: edge finding, region finding, texture,
shape from shading, shape from texture, shape from contour, and the
representations of surfaces and objects.  Much of the work described
was developed in the DARPA Image Understanding project.  In memory
of Max Clowes and David Marr.
%Y cost: $3.50, also available as NTIS report AD-A108191

%A Michael Brady
%A Berthold K.P. Horn
%T Rotationally Symmetric Operators for Surface Interpolation
%R AI Memo 654
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1981
%P 36
%K mit aim ail
%K vision
%X The use of rotationally symmetric operators in vision is reviewed and
conditions for rotational symmetry are derived for linear and
quadratic forms in the first and second partial directional
derivatives of a function f(x,y).  Surface interpolation is considered
to be the process of computing the most conservative solution
consistent with boundary conditions.  The "most conservative" solution
is modelled using the calculus of variations to find the minimum
function that satisfies a given performance index.  To guarantee the
existence of a minimum function, Grimson has recently suggested that
the performance index should be a semi-norm.  It is shown that all
quadratic forms in the second partial derivatives of the surface
satisfy this criterion.  The seminorms that are, in addition,
rotationally symmetric form a vector space whose basis is the square
Laplacian and the quadratic variation.  Whereas both seminorms give
rise to the same Euler condition in the interior, the quadratic
variation offers the tighter constraint at the boundary and is to be
preferred for surface interpolation.
%Y cost: $2.25, also available as NTIS report AD-A109032

%A Henry Lieberman
%T What Your Programs Are Doing
%R AI Memo 656
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D February 1982
%P 39
%K mit aim ail
%K visualization, example-based programming, debugging,
alpha beta search, interactive programming, graphics,
program testing, LISP
%X An important skill in programming is being able to visualize the
operation of procedures, both for constructing programs and debugging
them.  Tinker is a programming environment for Lisp that enables the
programmer to "see what the program is doing" while the program is
being constructed, by displaying the result of each step in the
program on representative examples.  To help the reader visualize the
operation of Tinker itself, an example is presented of how he or she
might use Tinker to construct an alpha-beta tree search program.
%Y cost: $2.25, also available as NTIS report AD-A113494

%A T. Poggio
%A C. Koch
%T Nonlinear Interactions in a Dendritic Tree: Localization, Timing and Role
in Information Processing
%R AI Memo 657
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D September 1981
%P 8
%K mit aim ail
%K microcircuits, synapses, nerve cells, nonlinear cables,
analog circuits
%X In a dendritic tree transient synaptic inputs activating ionic
conductances with an equilibrium potential near the resting potential
can veto very effectively other excitatory inputs.  Analog operations
of this type can be very specific with respect to relative locations
of the inputs and their timing.  We examine with computer experiments
the precise conditions underlying this effect in the case of a cat
retinal ganglion cell.  The critical condition required for strong and
specific interactions is that the peak inhibitory conductance change
must be sufficiently large, almost independently of other electrical
parameters.  In this case, a passive dendritic tree may perform
hundreds of independent analog operations on its synaptic inputs,
without requiring any threshold mechanism.
%Y cost: $1.50

%A Whitman Richards
%T How To Play 20 Questions With Nature and Win
%R AI Memo 660
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D December 1982
%P 26
%K mit aim ail
%K vision, information processing, perception, intrinsic
images, object recognition
%X The 20 Questions Game played by children has an impressive record of
rapidly guessing an arbitrarily selected object with rather few,
well-chosen questions.  This same strategy can be used to drive the
perceptual process, likewise beginning the search with the intent of
deciding whether the object is Animal-Vegetable-or Mineral.  For a
perceptual system, however,  several simple questions are required even
to make this first judgement as to the Kingdom the object belongs.
Nevertheless, the answers to these first simple questions, or their
modular outputs, provide a rich data base which can serve to classify
objects or events in much more detail than one might expect, thanks to
constraints and laws imposed upon natural processes and things. The
questions, then, suggest a useful set of primitive modules for
initializing perception.
%Y cost: $2.25

%A John M. Hollerbach
%T Workshop on the Design and Control of Dextrous Hands
%R AI Memo 661
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1982
%P 21
%K mit aim ail
%K robotics, end effectors, dextrous hands
%X The Workshop for the Design and Control of Dextrous Hands was held at
the MIT Artificial Intelligence Laboratory on November 5-6, 1981.
Outside experts were brought together to discuss four topics:
kinematics of hands, actuation and materials, touch sensing, and
control.  This report summarizes the discussions of the participants,
and attempts to identify a consensus on applications, mechanical
design, and control.
%Y cost: $2.25, also available as NTIS report AD-A114973

%A Anna R. Bruss
%A B.K.P. Horn
%T Passive Navigation
%R AI Memo 662
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1981
%P 20
%K mit aim ail
%K passive navigation, optical flow, time-varying imagery
%X A method is proposed for determining the motion of a body relative to
a fixed environment using the changing image seen by a camera attached
to the body.  The optical flow in the image plane is the input, while
the instantaneous rotation and translation of the body are the output.
If optical flow could be determined precisely, it would only have to
be known at a few places to compute the parameters of the motion.  In
practice, however, the measured optical flow will be somewhat
inaccurate.  It is therefore advantageous to consider methods which
use as much of the available information as possible.  We employ a
least-squares approach which minimizes some measure of the discrepancy
between the measured flow and that predicted from the computed motion
parameters.  Several different error norms are investigated.  In
general, our algorithm leads to a system of nonlinear equations from
which the motion parameters may be computed numerically.  However, in
the special cases where the motion of the camera is purely
translational or purely rotational, use of the appropriate norm leads
to a system of equation from which these parameters can be determined
in closed form.
%Y cost: $1.50, also available as NTIS report AD-A110070

%A W.E.L Grimson
%T The Implicit Constraints of the Primal Sketch
%R AI Memo 663
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D October 1981
%P 36
%K mit aim ail
%K primal sketch, zero crossings, surface consistency,
surface interpolation
%X Computational theories of structure-from-motion and stereo vision only
specify the computation of three-dimensional surface information at
points in the image at which the irradiance changes.  Yet, the visual
perception is clearly of complete surfaces, and this perception is
consistent for different observers.  Since mathematically the class of
surfaces which could pass through the known boundary points provided
by the stereo system is infinite and contains widely varying surfaces,
the visual system must incorporate some additional constraints besides
the known points in order to compute the complete surface.
%Y cost: $2.25, also available as NTIS report AD-A114789

%A Kenneth D. Forbus
%T Qualitative Process Theory
%R AI Memo 664
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D February 1982
%P 54
%K mit aim ail
%O See A.I. Memo 664A
%Y unavailable

%A Kenneth D. Forbus
%T Qualitative Process Theory
%R AI Memo 664A
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1983
%P 97
%K mit aim ail
%O See AI-TR-789
%Y cost: $3.00, unavailable except as NTIS report AD-A112225

%A Randall Davis
%T Expert Systems: Where Are We?  And Where Do We Go From Here?
%R AI Memo 665
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1982
%P 40
%K mit aim ail
%K expert systems, debugging, causality, structural models,
behavioral models
%O See ``The AI Magazine'', Spring 1982
%X Work on Expert Systems has received extensive attention recently,
prompting growing interest in a range of environments.  Much has been
made of the basic concept and of the rule-based system approach
typically used to construct the programs.  In this paper we review
what we know, assess the current prospects, and suggest directions
appropriate for the next steps of basic research.
%Y cost: $2.25

%A Michael Brady
%A W. Eric L. Grimson
%T The Perception of Subjective Surfaces
%R AI Memo 666
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1981
%P 48
%K mit aim ail
%K surface perception, subjective contours, edge detection, occlusion
%O See A.I. Memo 582 (never written)
%X It is proposed that subjective contours are an artifact of the
perception of natural three-dimensional surfaces.  A recent theory of
surface interpolation implies that "subjective surfaces" are
constructed in the visual system by interpolation between
three-dimensional values arising from interpretation of a variety of
surface cues.  We show that subjective surfaces can take any form,
including singly and doubly curved surfaces, as well as the commonly
discussed fronto-parallel planes.  In addition, it is necessary in the
context of computational vision to make explicit the discontinuities,
both in depth and in surface orientation, in the surfaces constructed
by surface interpolation.  It is proposed that subjective contours
form the boundaries of the subjective surfaces due to these
discontinuities.
%Y cost: $2.75, also available as NTIS report AD-A113495

%A David Allen McAllester
%T Reasoning Utility Package User's Manual, Version One
%R AI Memo 667
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1982
%P 56
%K mit aim ail
%K reasoning utilities, automated deduction, backtracking
congruence closures, theorem proving, truth maintenance, dependencies,
demonic invocation
%X RUP (Reasoning Utility Package) is a collection of procedures for
performing various computations relevant to automated reasoning.  RUP
contains a truth maintenance system (TMS) which can be used to perform
simple propositional deduction (unit clause resolution), to record
justifications, to track down underlying assumptions, and to perform
incremental modifications when premises are changed.  This TMS can be
used with an automated premise controller which automatically retracts
"assumptions" before "solid facts" when contradictions arise and
searches for the most solid proof of an assertion.  RUP also contains
a procedure for efficiently computing all the relevant consequences of
any set of equalities between ground terms.  A related utility
computes "substitution simplifications" of terms under an arbitrary
set of unquantified equalities and a user defined simplicity order.
RUP also contains demon writing macros which allow one to write
PLANNER like demons that trigger on various types of events in the
data base.  Finally there is a utility for reasoning about partial
orders and arbitrary transitive relations.  In writing all of these
utilities an attempt has been made to provide a maximally flexible
environment for automated reasoning.
%Y cost: $2.75, also available as NTIS report AD-A114756

%A W. Richards
%A H.K. Nishihara
%A B. Dawson
%T CARTOON: A Biologically Motivated Edge Detection Algorithm
%R AI Memo 668
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D June 1982
%P 24
%K mit aim ail
%K vision, vision algorithm, edge detection
%X Caricatures demonstrate that only a few significant "edges" need to be
captured to convey the meaning of a complex pattern of images
intensities.  The most important of these "edges" are image intensity
changes arising from surface discontinuities or occluding boundaries
The CARTOON algorithm is an attempt to locate these special intensity
changes using a modification of the zero-crossing coincidence scheme
suggested by Marr and Hildreth (1980).
%Y cost: $2.25

%A Steven W. Zucker
%A Kent A. Stevens
%A Peter T. Sander
%T The Relation Between Proximity and Brightness Similarity in Dot Patterns
%R AI Memo 670
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1982
%P 15
%K mit aim ail
%K vision, texture, grouping, gestalt, dot patterns
%X The Gestalt studies demonstrated the tendency to visually organize
dots on the basis of similarity, proximity, and global properties such
as closure, good continuation, and symmetry.  The particular
organization imposed on a collection of dots is thus determined by
many factors, some local, some global.  We discuss computational
reasons for expecting the initial stages of grouping to be achieved by
processes with purely local support.  In the case of dot patterns, the
expectation is that neighboring dots are grouped on the basis of
proximity and similarity of contrast, by processes that are
independent of the overall organization and the various global
factors.  We describe experiments that suggest a purely local
relationship between proximity and brightness similarity in perceptual
grouping.
%Y cost: $1.50

%A Demetri Terzopoulos
%T Multi-Level Reconstruction of Visual Surfaces: Variational Principles
and Finite Element Representations
%R AI Memo 671
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1982
%P 91
%K mit aim ail
%K computer vision, hierarchical representations,
variational principles, stereo, surface reconstruction, finite elements,
multi-level relaxation, interpolation
%X Computational modules early in the human vision system typically
generate sparse information about the shapes of visible surfaces in
the scene.  Moreover, visual processes such as stereopsis can provide
such information at a number of levels spanning a range of
resolutions.  In this paper, we extend this multi-level structure to
encompass the subsequent task of reconstructing full surface
descriptions from the sparse information.  We describe the three steps
of the mathematical development.  Examples of the generation of
hierarchies of surface representations from stereo constraints are
given.  Finally, the basic surface approximation problem is revisited
in a broader mathematical context whose implications are of relevance
to vision.
%Y cost: $3.00, also available as NTIS report AD-A115033

%A Daniel G. Theriault
%T A Primer for the Act-1 Language
%R AI Memo 672
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D April 1982
%P 94
%K mit aim ail
%K actors, parallelism, concurrency, programming languages,
programming language system, message passing
%X This paper describes the current design for the Act-I computer
programming language, and describes the Actor computational model,
which the language was designed to support.  It provides a perspective
from which to view the language, with respect to existing computer
language systems and to the computer system and environment under
development for support of the language.  The language is informally
introduced in a tutorial fashion and demonstrated through examples.
%Y cost: $3.00, also available as NTIS report AD-A115072

%A Rodney A. Brooks
%T Solving the Find-Path Problem by Representing Free Space as
Generalized Cones
%R AI Memo 674
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1982
%P 21
%K mit aim ail
%K robotics, find-path, collision avoidance, path planning,
generalized cones
%X Free space is represented as a union of (possibly overlapping)
generalized cones.  An algorithm is presented which efficiently finds
good collision free paths for convex polygonal bodies through space
littered with obstacle polygons.  The paths are good in the sense that
the distance of closest approach to an obstacle over the path is
usually far from minimal over the class of topologically equivalent
collision free paths.  The algorithm is based on characterizing the
volume swept by a body as it is translated and rotated as a
generalized cone and determining under what conditions one generalized
cone is a subset of another.
%Y cost: $2.25, also available as NTIS report AD-A115047

%A Tomaso Poggio
%A Kenneth Nielsen
%A Keith Nishihara
%T Zero-Crossings and Spatiotemporal Interpretation in Vision
%R AI Memo 675
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1982
%P 48
%K mit aim ail
%K interpolation, zero crossings, aliasing, electrical coupling
%X We will briefly outline a computational theory of the first stages of
human vision according to which (a) the retinal image is filtered by a
set of centre-surround receptive fields (of about 5 different spatial
sizes) which are approximately bandpass in spatial frequency and (b)
zero-crossings are detected independently in the output of each of
these channels.  Zero-crossings in each channel are then a set of
discrete symbols which may be used for later processing such as
contour extraction and stereopsis.  A formulation of Logan's
zero-crossing results is proved for the case of Fourier polynomials
and an extension of Logan's theorem to 2-dimensional functions is also
proved.
%Y cost: $2.75, also available as NTIS report AD-A117608

%A Kent A. Stevens
%T Implementation of a Theory for Inferring Surface Shape from Contours
%R AI Memo 676
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D August 1982
%P 27
%K mit aim ail
%K vision, surface perception, contours, shape
%X Human vision is adept at inferring the shape of a surface from the
image of curves lying across the surface.  The strongest impression of
3-D shape derives from parallel (but not necessarily equally spaced)
contours.  In (Stevens 1981a) the computational problem of inferring
3-D shape from image configurations is examined, and a theory is given
for how the visual system constrains the problem by certain
assumptions.  The assumptions are three: that neither the viewpoint
nor the placement of the physical curves on the surface is misleading,
and that the physical curves are lines of curvature across the
surface.  These assumptions imply that parallel image contours
correspond to parallel curves lying across an approximately
cylindrical surface.  Moreover, lines of curvature on a cylinder are
geodesic and planar.  These properties provide strong constraint on
the local surface orientation.  We describe a computational method
embodying these geometric constraints that is able to determine the
surface orientation even in places where locally it is very weakly
constrained, by extrapolatating from places where it is strongly
constrained.  This computation has been implemented, and predicts
local surface orientation that closely matches the apparent
orientation.  Experiments with the implementation support the theory
that our visual interpretation of surface shape from contour assumes
the image contours correspond to lines of curvature.
%Y cost: $2.25, also available as NTIS report AD-A127285

%A Boris Katz and Patrick H. Winston
%T Parsing and Generating English Using Communicative Transformations
%R AI Memo 677
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1982
%P 18
%K mit aim ail
%K parsing, generation, natural language, semantic networks,
commutative transformations, language understanding
%X This paper is about an implemented natural language interface that
translates from English into semantic net relations and from semantic
net relations back into English.  The parser and companion generator
were implemented for two reasons: (a) to enable experimental work in
support of a theory of learning by analogy; (b) to demonstrate the
viability of a theory of parsing and generation built on commutative
transformations.  The learning theory was shaped to a great degree by
experiments that would have been extraordinarily tedious to perform
without the English interface with which the experimental data base
was prepared, revised, and revised again.  Inasmuch as current work on
the learning theory is moving toward a tenfold increase in data-base
size, the English interface is moving from a facilitating role to an
enabling one.  The parsing and generation theory has two particularly
important features: (a) the same grammar is used for both parsing and
generation; (b) the transformations of the grammar are commutative.
%Y cost: $1.50, also available as NTIS report AD-A117440

%A Patrick H. Winston
%T Learning by Augmenting Rules and Accumulating Censors
%R AI Memo 678
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1982
%P 23
%K mit aim ail
%K learning, artificial intelligence, analogy
%O Revised September 1982
%X This paper is a synthesis of several sets of ideas: ideas about
learning from precedents and exercises, ideas about learning using
near misses, ideas about generalizing if-then rules, and ideas about
using censors to prevent procedure misapplication.  The synthesis
enables two extensions to an implemented system that solves problems
involving precedents and exercises and that generates if-then rules as
a byproduct.  These extensions are as follows:  If-then rules are
augmented by unless conditions, creating augmented if-then rules.  An
augmented if-then rule is blocked whenever facts in hand directly
demonstrate the truth of an unless condition. When an augmented
if-then rule is used to demonstrate the truth of an unless condition,
the rule is called a censor.  Like ordinary augmented if-then rules,
censors can be learned.  Definition rules are introduced that
facilitate graceful refinement.  The definition rules are also
augmented if-then rules.  They work by virtue of unless entries that
capture certain nuances of meaning different from those expressible by
necessary conditions.  Like ordinary augmented if-then rules,
definition rules can be learned. The strength of the ideas is
illustrated by way of representative experiments.  All of these
experiments have been performed with an implemented system.
%Y cost: $2.25, also available as NTIS report AD-A117439

%A Patrick H. Winston
%A Thomas O. Binford
%A Boris Katz
%A Michael Lowry
%T Learning Physical Descriptions from Functional Definitions,
Examples, and Precedents
%R AI Memo 679
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D November 1982
%P 23
%K mit aim ail
%K learning, form and function
%O Revised January 1983
%X It is too hard to tell vision systems what things look like.  It is
easier to talk about purpose and what things are for.  Consequently,
we want vision systems to use functional descriptions to identify
things, when necessary, and we want them to learn physical
descriptions for themselves, when possible.  This paper describes a
theory that explains how to make such systems work.  The theory is a
synthesis of two sets of ideas: ideas about learning from precedents
and exercises developed at MIT, and ideas about physical description
developed at Stanford.  The strength of the synthesis is illustrated
by way of representative experiments.  All of these experiments have
been performed with an implemented system.
%Y cost: $2.25, also available as NTIS report AD-A127047

%A Richard C. Waters
%T LETS, An Expressional Loop Notation
%R AI Memo 680A
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D October 1982
%P 57
%K mit aim ail
%K loops, programming languages, LISP
%Y unavailable except as NTIS report AD-A122108

%A Gerald Barber
%T Supporting Organizational Problem Solving with a Workstation
%R AI Memo 681
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D July 1982
%P 30
%K mit aim ail
%K problem solving, office information systems, workstations,
OMEGA, viewpoints, office semantics, change and contradiction,
office automation
%X This paper describes an approach to supporting work in the office.
Using and extending ideas from the field of Artificial Intelligence
(AI) we describe office work as a problem solving activity.  A
knowledge embedding language called Omega is used to embed knowledge
of the organization into an office worker's workstation in order to
support the office worker in his or her problem solving.  A particular
approach to reasoning about change and contradiction is discussed.
This approach uses Omega's viewpoint mechanism.  Omega's view point
mechanism is a general contradiction handling facility.  Unlike other
knowledge representation systems, when a contradiction is reached the
reasons for the contradiction can be analyzed by the deduction
mechanism without having to resort to a backtracking mechanism.  The
view point mechanism is the heart of the Problem Solving Support
Paradigm.  An example is presented where Omega's facilities are used
to support an office worker's problem solving activities.  The example
illustrates the use of view points and of Omega's capabilities to
reason about it's own reasoning process.
%Y cost: $2.25, also available as NTIS report AD-A130481

%A Tomaso Poggio
%T Visual Algorithms
%R AI Memo 683
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%K mit aim ail
%I Artificial Intelligence Laboratory, Massachusetts Institute of Technology
%D May 1982
%P 28
%K mit aim ail
%K polynomial algorithms, parallel/serial, neural hardware,
perceptrons, nonlinear mappings
%X Nonlinear, local and highly parallel algorithms can perform several
simple but important visual computations. Specific classes of
algorithms can be considered in an abstract way. I study here the
class of polynomial algorithms to exemplify some of the important
issues for visual processing like linear vs. nonlinear and local vs.
global. Polynomial algorithms are a natural extension of Perceptrons
to time dependent grey level images. Although they share most of the
limitations of Perceptrons, they are powerful parallel computational
devices.  Several of their properties are characterized and especially
(a) their equivalence with Perceptrons for geometrical figures and (b)
the synthesis of nonlinear algorithms (mappings) via associative
learning. Finally, the paper considers how algorithms of this type
could be implemented in nervous hardware, in terms of synaptic
interactions strategically located in a dendritic tree.  The
implementation of three specific algorithms is briefly outlined:
(a) direction sensitive motion detection, (b) detection of
discontinuities in the optical flow, (c) detection and localization of
zero-crossings in the convolution of the image with the Laplacian (of
a Gaussian). In the appendix, another (nonlinear) differential
operator, the second directional derivative along the gradient, is
briefly discussed as an alternative to the Laplacian.
%Y cost: $2.25, also available as NTIS report AD-A127251