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AIList Digest Volume 4 Issue 007
AIList Digest Wednesday, 15 Jan 1986 Volume 4 : Issue 7
Today's Topics:
Seminars - Reasoning About Hard Objects (BBN) &
LOGIN: A Logic Programming Language with Inheritance (MIT) &
Temporal Reasoning and Default Logics (SU) &
LISP/Prolog Memory Performance (Ames)
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Date: 9 Dec 1985 12:10-EST
From: Brad Goodman <BGOODMAN at BBNG>
Subject: Seminar - Reasoning About Hard Objects (BBN)
[Forwarded from the MIT bboard by SASW@MIT-MC.]
BBN Laboratories
Science Development Program
AI Seminars
Speaker: Ernest Davis
NYU
Title: Issues in Reasoning about Hard Objects
Date: Monday, December 16th, 10:30a.m.
Place: BBN Labs, 10 Moulton Street, 3rd floor large conference room
Abstract
The physics of rigid solid objects raises two serious problems which have not
been addressed in previous spatial and physical reasoning programs. Firstly,
the physical properties of solid objects are sensitive to very slight
variations in shapes. Therefore, when an ideal shape is used to
approximate a real shape, the accuracy of the approximation must be
tightly bounded. Secondly, the method of reasoning used by both Forbus
and DeKleer of going from one critical point to the next is not, in
general, appropriate. Frequently, as in reasoning about a ball going
down a funnel, one is interested only in the final outcome (the ball
goes out the funnel) and not in any of the intermediate critical points
(collisions between the ball and the funnel). However, it is difficult
to state axioms that assert global relationships of this sort in a way
that allows them to be used in cases where additional objects enter the
picture.
------------------------------
Date: Thu 9 Jan 86 13:37:32-EST
From: Susan Hardy <SH@XX.LCS.MIT.EDU>
Subject: Seminar - LOGIN: A Logic Programming Language with Inheritance (MIT)
[Forwarded from the MIT bboard by SASW@MC.LCS.MIT.EDU.]
DATE: Thursday, January 16, 1986
TIME: 3:00 p.m. - Refreshments
3:15 p.m. - Lecture
PLACE: NE43-512A
LOGIN:
A LOGIC PROGRAMMING LANGUAGE
WITH BUILT-IN INHERITANCE
Hassan Ait-Kaci
A.I. Program
MCC, Austin, Texas
Since the early days of research in Automated Deduction, inheritance
has been proposed as a means to capture a special kind of information;
viz., taxonomic information. For example, when it is asserted that
"whales are mammals", we understand that whatever properties mammals
possess should also hold for whales. Naturally, this meaning of
inheritance can be well captured in logic by the semantics of logical
implication. However, this is not operationally satisfactory.
Indeed, in a first-order logic deduction system realizing inheritance
as implication, inheritance from "mammal" to "whale" is achieved by an
inference step. But this special kind of information somehow does not
seem to be meant as a deduction step---thus lengthening proofs.
Rather, its purpose seems to be to accelerate, or focus, a deduction
process---thus shortening proofs.
In this talk, I shall argue that the syntax and operational
interpretation of first-order terms can be extended to accommodate for
taxonomic ordering relations between constructor symbols. As a
result, I shall propose a simple and efficient paradigm of unification
which allows the separation of (multiple) inheritance from the logical
inference machinery of Prolog. This yields more efficient
computations and enhanced language expressiveness. The language thus
obtained, called LOGIN, subsumes Prolog, in the sense that
conventional Prolog programs are equally well executed by LOGIN.
I shall start with motivational examples, introducing the flavor of
what I believe to be a more expressive and efficient way of using
taxonomic information, as opposed to straight Prolog. Then, I shall
give a quick formal summary of how first-order terms may be extended
to embody taxonomic information as record-like type structures,
together with an efficient type unification algorithm. This will lead
to a technical proposal for integrating this notion of terms into the
SLD-resolution mechanism of Prolog. With examples, I shall illustrate
a LOGIN interpreter.
Host: Rishiyur Nikhil
(617)253-0237
Nikhil@mit-xx.arpa
------------------------------
Date: 13 Jan 86 1659 PST
From: Vladimir Lifschitz <VAL@SU-AI.ARPA>
Subject: Seminar - Temporal Reasoning and Default Logics (SU)
Next nonmotonic reasoning meeting:
A Review and Critique of:
"Temporal Reasoning and Default Logics"
by Steve Hanks and Drew McDermott
Yale/CSD/RR #430
October 1985
by Benjamin Grosof, inquisitioner
Thursday, January 16, 4pm
MJH 252
Hanks and McDermott in their recent Yale Tech Report pose an example
problem in temporal reasoning and claim that none of the leading
formalisms for default reasoning (namely Reiter's Default Logic,
McDermott and Doyle's modal Non-Monotonic Logic, and Circumscription)
adequately capture the type of non-monotonic reasoning that is (what
they claim is) desirable in the example. They give an algorithm which
does. They go on to conclude rather pessimistically that there seems
to be some inherent problem in the semantics of all three default
formalisms.
In this talk, I review their paper, including their temporal logic. I
argue that their example in particular is interesting and suggestive,
but that the semantical difficulty that they emphasize arises from an
underspecification of the problem. I will go on to suggest how indeed
to represent the additional CRITERION satisfied by their algorithm
(but not by their formulations in default formalisms). I show how
Vladimir's new circumscription presented in our fall sessions of the
non-monotonic reasoning seminar can solve the representational problem
they pose. I argue that circumscription, because it can incorporate
certain kinds of preferences among competing extensions via
prioritization, has an advantage over the other two default
formalisms, and promises to be able to represent the CRITERION more
generally than their algorithm does. I also discuss how their
temporal formalism occupies an intermediate place between STRIPS and
situation calculus.
------------------------------
Date: Tue, 14 Jan 86 21:47:09 pst
From: eugene@AMES-NAS.ARPA (Eugene Miya)
Subject: Seminar - LISP/Prolog Memory Performance (Ames)
National Aeronautics and Space Administration
Ames Research Center
SEMINAR ANNOUNCEMENT
Joint Ames AI Forum/RCR Branch
SPEAKER: Evan Tick
Computer Systems Laboratory
Stanford University
TOPIC: Memory Performance of Lisp and Prolog Programs
ABSTRACT: This talk presents a comparison between Lisp and Prolog
architectures based on memory performance. A subset of the Gabriel
benchmarks was translated into Prolog, compiled into the Warren Abstract
Machine instruction set and emulated. The programs were also measured with
an instrumented Common Lisp targeted to a Series 9000/HP237. Memory usage
statistics indicate how the two langauges do fundamental computations
different ways with varying efficiency.
DATE: 28 January 1986 TIME: 1030 AM BLDG: 172 ROOM: 233
Tuesday
POINT OF CONTACT: E. Miya PHONE NUMBER: (415)-694-6453
emiya@ames-vmsb
I am current attending a conference, please send mail or contact my office
mate.
VISITORS ARE WELCOME: Register and obtain vehicle pass at Ames Visitor
Reception Building (N-253) or the Security Station near Gate 18. See map
below. Do not use the Navy Main Gate.
Non-citizens (except Permanent Residents) must have prior approval from the
Director's Office one week in advance. Submit requests to the point of
contact indicated above. Non-citizens must register at the Visitor
Reception Building. Permanent Residents are required to show Alien
Registration Card at the time of registration.
------------------------------
End of AIList Digest
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