Dialogue Understanding based on Situation Semantics and Pragmatics
Hidetosi SIRAI, Ken-ichiro SHIRAI, Imani IKUMI and Toshiyuki TONOIKE
School of Computer and Cognitive Sciences, Chukyo University
Tokodate 101, Kaizu-cho, Toyota, 470-03, JAPAN
e-mail: sirai@sccs.chukyo-u.ac.jp
We have been studying a dialogue understanding model based on
Situation Semantics. The object is to investigate how the context
including the beliefs of conversational participants are developed
under the grammatical and pragmatic constraints.
Last year, we studied the constraints of so-called presupposition.
We analyzed the problems around presupposition, especially on the
projection problem which is the relation between the presupposition of
the whole sentence and those of its parts. Furthermore, we formalized
the presupposition from the point of inverse information, and described
some related phenomena.
This year, we studied `definiteness' and `negation' in Japanese,
because our team's common theme is `Representation and Understanding
of Concepts', and definiteness and negation are the concepts which
are hard to understand and should be investigated in more detail.
Furthermore, we studied on the descriptions of conceptual structures
in lexicon in order to make a dialogue system.
Our contributions are summarized as follows:
{1. Research of Definiteness and Presupposition}
In this research, the notion of definiteness in Japanese is investigated
employing recent outcomes of dynamic semantics (Dynamic Predicate Logic
and Update Semantics). Based on the dynamic treatment of definiteness
from the information-theoretic perspective of meaning, existential
presupposition of Japanese noun-phrases will be given a more
discourse-oriented account.
{2. Research of Negation in Japanese}
The purpose of this research is to clarify how meanings of
negative expressions are constrained by situations in which
they are used, and to discuss what constraints there are.
Negation has traditionally been analyzed by syntactic or semantic
approaches. However, it seems that only with these approaches we
cannot explain why (1) sounds strange.
John-wa rappa-wo 2-kai narasa-nak-atta. (1)
John-TOP trumpet-ACC 2-times blow-NEG-PAST
`John did not blow the trumpet twice'
The strangeness of (1) is not from syntactic or semantic reasons but
from some pragmatic reason, because (1) sounds natural if it is
used in appropriate situations such as the one in which although John
had been ordered to blow the trumpet 12 times, he did it
only 10 times. This indicates that we have to investigate what constrains
induce or block the reading of propositional or predicative negation.
The following results have been obtained so far.
Let S be a sentence with negation and quantifier(s), and S' a sentence
which is the same as S, except that it is lack of negation.
In each case, we can see situations as helping calculate the content of S.
{3. Research on Lexical Conceptual Structure}
In this study, we have considered how to compile a lexicon for a
natural language in general, and lexical extensions in particular. Most
lexical items can be polysemous; some of their meanings are lexicalized,
i.e., registered in the lexicon, some lexical items can be used in an
extensive way, often in a heavily context-dependent way. we have tried
to capture such extension possibilities and proposed to store such
knowledge as heuristics, as extension-patterns of semantic features in
the lexicon. With the aid of such heuristics, we can obtain a lexicon
which is generative in the sense that when we cannot interpret
utterances by static lexical descriptions, we can generate tentatively
extended meanings. For example, a group of nouns which are place
names (LOC-ation) can refer to people live there (ORG-ination). Also
we assume lexical conceptual structures which consists of a verbal element,
nouns/noun phrases and possibly adverbial elements.
In the next fiscal year, we will consider the relationships between
lexical descriptions and lexical conceptual structures and examine the
structured lexicon and the mechanism of forming and processing concepts.
Keywords: definiteness, presupposition, dynamic semantics, negation, quantifier and situation, generative lexicon