mwang@watmath.UUCP (mwang) (05/30/84)
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- Wednesday, June 6, 1984.
Dr. G. Hirst of the University of Toronto will speak on
``Semantic Interpretation Against Ambiguity.''
TIME: 3:30 PM
ROOM: MC 5158
ABSTRACT
We describe a new approach to semantic interpretation
in natural language understanding, and mechanisms for
both lexical and structural disambiguation that work in
concert with the semantic interpreter.
Traditionally, translation from the parse tree of a
sentence to a semantic representation (such as frames
or procedural semantics) has always been the most ad
hoc part of natural language understanding systems.
However, recent advances in linguistics, most notably
the system of formal semantics known as Montague seman-
tics, suggest ways of putting semantic interpretation
onto a cleaner and firmer foundation.
Absity, the system we describe, is a Montague-inspired
semantic interpreter. Like Montague formalisms, our
semantics is compositional by design and is strongly
typed, with semantic rules in one-to-one correspondence
with the meaning-affecting rules of a Marcus parser.
We have replaced the Montague semantic objects -- func-
tors and truth conditions -- with elements of the frame
language Frail. Absity's partial results are always
well-formed Frail objects.
A semantic interpreter must be able to provide feedback
to the parser to help it handle structural ambiguities.
In Absity, this is done by the ``Semantic Enquiry
Desk,'' a process that answers the parser's questions
on semantic preferences. Disambiguation of word senses
and of case slots is done by a set of procedures, one
per word or slot, each of which determines its correct
sense in cooperation with the others. A partially
disambiguated procedure's remaining possibilities are
well-formed Frail objects that can be seen and used by
May 30, 1984
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other processes, including the Semantic Enquiry Desk,
just as a person can see many of the details of a part-
ly developed ``instant'' photograph.
It is from the fact that partial results are always
well-formed semantic objects that the system gains much
of its power. This, in turn, comes from the strict
correspondence between syntax and semantics in Absity.
The result is a foundation for semantic interpretation
that we believe to be superior to previous approaches.
Coffee and refreshments will be served at 3:00 PM.
May 30, 1984