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Titles and abstracts

Here they are.  The lectures are independent and can be given
in whatever order seems most suitable to the audiences.

NON-MONOTONIC REASONING

Logical deduction is monotonic in the set of premises.  Thus if a
sentence  $p$ is deducible from a set  $A$ of sentences and $B$ includes
$A$,  then $p$ is deducible from $B$.  Ordinary human reasoning does
not always have this property, and artificially intelligent systems
also need to supplement deduction by non-monotonic reasoning.
This involves drawing a conclusion from a set of premisses that would
not necessarily be drawn from a larger set.  Since the late 1970s
there have been both expert systems that use non-monotonic reasoning
and mathematical theories of it.  This lecture treats the circumscription
mode of non-monotonic reasoning and some applications to formalizing
common sense knowledge and reasoning.  The basic idea of circumscription
is to assume that certain predicates have minimal extensions compatible
with the premisses.  It is therefore a form of Ockham's razor.
\vfill\eject\end

ELEPHANT 2000 - A PROGRAMMING LANGUAGE WITH SPEECH ACTS

\noindent Abstract: Elephant 2000 is a vehicle for some ideas about
programming language features.  We expect these features to be
valuable in writing and verifying programs that interact with
people (e.g. transaction processing) or interact with programs belonging
to other organizations (e.g. electronic data interchange)
\hfill\break 1. Communication inputs and outputs are in an I-O
language whose sentences are meaningful speech acts approximately
in the sense of philosophers and linguists.  These include
questions, answers, offers, acceptances, declinations, requests,
permissions and promises.
\hfill\break 2. The correctness of programs is partially defined in
terms of proper performance of the speech acts.  Answers should
be truthful, and promises should be kept.  Sentences of logic expressing
these forms of correctness can be generated automatically
from the form of the program.
\hfill\break 3. Elephant source programs may not need data
structures, because they can refer directly to the past.  Thus a
program can say that an airline passenger has a reservation if he
has made one and hasn't cancelled it.
\hfill\break 4. Elephant programs themselves will be represented as
sentences of logic.  Their properties follow from this
representation without an intervening theory of programming or
anything like Hoare axioms.
\hfill\break 5. Elephant programs that interact non-trivially with
the outside world can have both {\it illocutionary} and {\it perlocutionary}
specifications, i.e. behavioral specifications relating inputs and outputs,
and specifications concerning what they accomplish in the world.

Some Expert Systems Need Common Sense

	An {\it expert system} is a computer program intended to embody the
knowledge and ability of an expert in a certain domain.  The ideas behind
them and several examples have been described in other lectures in this
symposium.  Their performance in their specialized domains are often
very impressive.  Nevertheless, hardly any of them have certain
{\it common sense} knowledge and ability possessed by any non-feeble-minded
human.  This lack makes them ``brittle''.  By this is meant that they are
difficult to extend beyond the scope originally contemplated by their
designers, and they usually don't recognize their own limitations.
Many important applications will require common sense abilities.  The object
of this lecture is to describe common sense
 abilities and the problems that require them.