Table Of ContentSPEECH AND
HUMAN-MACHINE
DIALOG
THE KLUWER INTERNATIONAL SERIES IN
ENGINEERING AND COMPUTER SCIENCE
SPEECH AND
HUMAN-MACHINE
DIALOG
by
Wolfgang Minker
University of Ulm
Germany
Samir Bennacef
Vecsys
France
KLUWER ACADEMIC PUBLISHERS
NEW YORK,BOSTON, DORDRECHT, LONDON, MOSCOW
eBookISBN: 1-4020-8037-9
Print ISBN: 1-4020-8036-0
©2004 Springer Science + Business Media, Inc.
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Boston
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Contents
Preface vii
1. INTRODUCTION 1
1 Language 2
2 Dialog and Computer 3
3 Human-Machine Spoken Language Dialog 4
4 Spoken Language Dialog System 10
5 Projects and Research Applications 10
2. ROBUSTSPOKEN LANGUAGE UNDERSTANDING 13
1 Introduction 13
2 Case Grammar Formalism 14
3 Case Grammar in the LIMSI-L’ATIS System 15
4 Conclusion 21
3. SPOKEN LANGUAGE DIALOG MODELING 23
1 Introduction 23
2 Task Modeling 23
3 Human-Machine Spoken Language Dialog Modeling 29
4 Dialog System Example 73
5 Conclusion 79
4. CONCLUSION 81
References 85
Index 91
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Preface
The conjunction of several factors having occurred throughout the past
few years will make humans significantly change their behavior vis-à-vis ma-
chines. In particular the use of speech technologies will become normal in
the professional domain, but also in everyday life. The performance of speech
recognition components has significantly improved: only within ten years we
have passed from systems able to recognize isolated words uttered by a single
speaker using a limited lexicon of around 50 words to systems able to recog-
nize continuous speech with an unlimited vocabulary uttered by any speaker;
or to systems able to carry a spontaneous dialog with a vocabulary of a few
thousands of words over the telephone, on a well-defined topic (e.g., infor-
mation on train or airplane schedules). The development of microelectronics,
considered to be at the origin of these significant results, also favors hard-
ware miniaturization enabling the integration of particularly time and memory
consuming signal processing algorithms into standard processors and portable
systems. Finally, the expanding computer and telephone networks allow the
general public an immediate location-independent access to large databases.
Under these circumstances, the state-of-the-art of research and achieve-
ments in the domain of human-machine spoken language dialog systems, pro-
posed by Wolfgang Minker and Samir Bennacef, seems particularly relevant.
In fact, speech enables access to various information services from a simple
standard telephone: the number of calls (up to one and a half million) received
per month by systems developed at Philips, CSELT, Nuance, etc., shows the
adequacy of these vocal servers to the user needs. Speech, combined with a
touch screen, also improves the communication with information terminals,
rendering them more natural, effective and fast.
However, the use of human-machine spoken language dialog systems is
still not generalized. This may be due to the fact that for a long time, a low
viii SPEECH AND HUMAN-MACHINE DIALOG
word error rate has been considered sufficient for integrating a speech recog-
nition component into an end-to-end human-machine interface. The impor-
tance of higher language levels including understanding and dialog have been
neglected. In fact, while significant progress has been made in speech recog-
nition, the results achieved by the syntaxico-semantic and pragmatic analy-
sis components and by the modeling of corresponding knowledge were not
likewise convincing. It was generally assumed that artificial intelligence tech-
niques only validated on text data could directly be applied to spoken language
processing. This, however, turned to ignore the specificity of spoken language,
in particular its high variability, and the variety of the requiredknowledge.
In this perspective, the book of Wolfgang Minker and Samir Bennacef rep-
resents a remarkable progress for at least two reasons. Firstly, because it places
a focus on the need for a correct modelization of the higher (semantic and prag-
matic) speech levels; secondly, because it describes in detail a very interesting
process of dialog modeling, which has been integrated in several prototype
demonstrators.
With respect to the first issue, the work underlines the importance of a se-
manticrepresentation well adapted to the processing of spoken language utter-
ances, that does not always respect the structure of the written language. One
suggested formalism has been an extension of the case grammars that allows
the system to cope with the dislocated and asyntactic character of speech. The
choice of the semantic cases is illustrated by a description of the air travel in-
formation system L’ATIS, a French version of the American ATIS (Air Travel
Information Services) application introduced by DARPA (Defense Research
Projects Agency) for the test campaigns of spoken language dialog systems.
With respect to the second issue, after a presentation of the different state-
of-the-artdialog model types (structural, plan-directed, logical, task-directed),
the book exhaustively describes a dialog model that is related to the structural
models having their origin in linguistic studies. This model, based on dialog
acts, is clearly different from the task model. Such a distinction allows for
a greater genericity. A hierarchical representation of the different dialog acts
allows a refined dialog control and anticipation of exchanges, whilst leaving
more initiative to the user. Several examples illustrate the different function-
alities of such a model in a representative application for information requests
for train schedules, fares and ticket reservation at the SNCF (French national
railway company).
It should be noted that the research described by the authors on understand-
ing and dialog modeling constitutes an essential precondition to a generalized
use of spoken language dialog technologies in systems designed for the gen-
eral public. The presented approaches led to several prototypes using different
languages (French and English) for different information retrieval tasks (train
and plane schedules, ticket reservation), which underlines the advantages of
PREFACE ix
the proposed choices. One of the prototypes developed within the framework
of the European project ESPRIT No 9075 Mask (Multimodal Multi-media Au-
tomated Service Kiosk) has been tested by more than 200 selected people in a
Parisian train station.
The care of the authors to situate their approaches in an historical context
and to compare them with the most outstanding international achievements in
the field, not only makes this work a reference for subsequent developments,
but also constitutes a solid basis for a thorough teaching in applied linguistics,
cognitive sciences, artificial intelligence and engineering science.
Françoise NÉEL
Head “Speech Communication” Group (1985-1994)
Head Multimodal Communication Platform Project of the Human-Machine
Communication Department, LIMSI-CNRS, Orsay, France (1994-2000)
