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Date: Thu, 16 Jan 86 08:53:12 est

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Subject: AIList Digest   V4 #7
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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)

----------------------------------------------------------------------

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 <[email-masked]>
Subject: Seminar - LOGIN: A Logic Programming Language with Inheritance (MIT)

       [Forwarded from the MIT bboard by [email-masked].]

                      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
              [email-masked]

------------------------------

Date: 13 Jan 86  1659 PST
From: Vladimir Lifschitz <[email-masked]>
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: [email-masked] (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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