LINGUIST List 15.2479

Tue Sep 7 2004

Diss: Comp Ling/Pragmatics: Purver: 'The Theory...'

Editor for this issue: Takako Matsui <>


  1. mpurver, The Theory and Use of Clarification Requests in Dialogue

Message 1: The Theory and Use of Clarification Requests in Dialogue

Date: Tue, 7 Sep 2004 15:52:31 -0400 (EDT)
From: mpurver <>
Subject: The Theory and Use of Clarification Requests in Dialogue

Institution: University of London
Program: Computational Linguistics
Dissertation Status: Completed
Degree Date: 2004

Author: Matthew Purver 

Dissertation Title: The Theory and Use of Clarification Requests in

Dissertation URL:

Linguistic Field: Computational Linguistics, Pragmatics, Semantics,
Syntax, Text/Corpus Linguistics

Subject Language: English (code: ENG)

Dissertation Director 1: Jonathan Ginzburg

Dissertation Abstract: 

Clarification requests are an important, relatively common and yet
under-studied dialogue device allowing a user to ask about some
feature (e.g. the meaning or form) of an utterance, or part
thereof. They can take many different forms (often highly elliptical)
and can have many different meanings (requesting various types of
information). This thesis combines empirical, theoretical and
implementational work to provide a study of the various types of
clarification request that exist, give a theoretical analysis thereof,
and show how the results can be applied to add useful capabilities to
a prototype computational dialogue system.

A series of empirical studies (corpus-based and experimental) are
described which establish a taxonomy of the possible types of
clarification request together with information about their meaning
and usage, about the phrase types and conditions that trigger them and
their particular forms and interpretations, and about the likely
methods of responding to them. A syntactic and semantic analysis
using the HPSG framework is given which extends the work of (Ginzburg
& Cooper, 2004) to cover the main classes of the above taxonomy, and
to account for the clarificational potential of those word and phrase
types which commonly cause clarification requests. This is shown to
have interesting implications for the semantics of various lexical and
phrasal types, in particular suggesting that noun phrases be given a
simple witness-set based representation.

Finally, the theoretical analysis and empirical findings are applied
within a HPSG grammar and a prototype text-based dialogue system,
CLARIE. Implemented in Prolog using the TrindiKit, the system
combines the information-state-based dialogue management of GoDiS
(Larsson et al., 2000) and the HPSG-based ellipsis resolution of
SHARDS (Ginzburg et al., 2001) and adds the capability to interpret
and respond to user clarification requests, and generate its own
clarifications where necessary to deal with incomprehensible or
contradictory input, resolve unknown or ambiguous reference, and learn
out-of-vocabulary words.
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