LINGUIST List 13.2219

Wed Sep 4 2002

Review: Syntax: Kempson, Meyer-Viol & Gabbay (2001)

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  1. Liu Haitao, Kempson, Meyer-Viol & Gabbay (2001) Dynamic Syntax

Message 1: Kempson, Meyer-Viol & Gabbay (2001) Dynamic Syntax

Date: Wed, 04 Sep 2002 00:34:28 +0000
From: Liu Haitao <htliuyeah.net>
Subject: Kempson, Meyer-Viol & Gabbay (2001) Dynamic Syntax

Kempson, Ruth, Wilfried Meyer-Viol, and Dov Gabbay (2001)
Dynamic Syntax: The Flow of Language Understanding. Blackwell
Publishers, xii+348pp, paperback ISBN 0-631-17613-6, $34.95.

Book Announcement on Linguist:
http://linguistlist.org/get-book.html?BookID=2742 


LIU Haitao, unaffiliated scholar

[This review was originally submitted on Feb. 8, 2002, but did
not reach us. The reviewer resent the review on Sept. 3, 2002.
We are sorry for the delay. --Eds.]

GENERAL SYNOPSIS

The book under review wants to develop a formal framework of human
language understanding from a common-sense viewpoint. This method and
assumption are very different from those well-established approaches,
which generally are static with a characterization of strings and some
surface structure and fixed interpretation. On the contrary, this
theory does not characterize the surface structure of a sentence, but
tries to assign an interpretation to a string of words in a left to
right fashion. In other words, this new model takes information from
words, pragmatic processes and general rules, and derives partial tree
structures that represent the underspecified content of the string,
and finally gets some representation in logical form.

We can call such process dynamic, because structures grow from some
initial skeletal form of interpretation to some more richly structured
object from which a full interpretation of the sentence can be derived
by logical means. In this model, the progressive product of partial
tree structures is a very important concept, it reflects three
properties central of natural language processing:

1. The parsing process is goal-directed, the goal being to establish
some logical form as representation of a propositional content for
some sentence.

2. The information needed to establish such interpretation is
progressively accumulated across the left-right sequence until the
goal is achieved.

3. The specification of interpretation provided by a sequence of words
may be less than the interpretation assigned to that sequence, and in
such cases interaction with pragmatic actions is needed to update the
lexical specifications provided.

Another important notion is tree growth, which involves two primary
concepts: growth of tree structure by addition of nodes and fixing of
tree relations, growth of decorations on a node with progressive
replacement of requirements by annotations.

This book sets out an original model of the dynamics of language
processing, which can be used to explain the structural properties of
language in a simple and elegant way. The model is introduced both
informally and formally, and is applied to many languages with
different features of the syntactic structures. Following the short
history of this theory and method, we can see that this book is an
interdisciplinary product of linguistics, applied logic, and
philosophy of language. Alongside formal definitions, the authors use
step-by-step derivations and detailed lexical definitions to
illustrate this new form of syntactic analysis and to show how the
model can be applied to a broad range of languages. In this way, the
reader gets a sense of the rich potential the framework provides for
general application to linguistic analysis.

CHAPTER CONTENT

Chapter 1 (Towards a Syntactic Model of Interpretation): What is the
notion 'Knowing a language'? The authors begin themselves book from
the common-sense view of this banal notion. According to the authors,
most linguists do not construct themselves theories following the
general view. This book is to be an implicit plea to return to the
common-sense view. Using 5 subchapters titled 'Natural Language as
Formal Language?', 'Underspecification in Language Processing', 'The
Representational Theory of Mind', 'Pronominal Anaphora: Semantic
Problems', 'The Anaphora Solution - Towards a Representational
Account', the authors presents the fundamental difference between
dynamic and traditional syntax, and skeletal structure of this
book. Some main topics, which will be touched in this book, are also
summarized in this chapter, such as the difficult anaphora and
long-distance dependency problems in language processing/parsing. In
many points, the authors emphasize that the process of understanding a
natural language string should be defined as a process of
incrementally constructing representations. The view undoubtedly is a
departure from the general assumption that natural language systems
are formal languages whose syntactic properties are defined over
strings of words or sentences with semantic interpretation defined
relative to their syntactic structure. 

Chapter 2 (The General Framework): As the mentioned above, the authors
aim at defining a formal model of the left-to-right process of natural
language understanding. For this reason, this chapter is the core of
the book, presenting the important aspects of dynamic syntax. The
so-called left-to-right process can be classified as a two-step
process: First, a tree structure is induced from the linear sequence
of words, with words introducing tree structure and lambda terms as
annotations for nodes. Secondly, with the final tree reflecting the
interpretation of the sentence, the non-terminal nodes are
consecutively annotated - with 'reductions' - through a bottom-up
process, that leads to a propositional formula as annotation at the
root node. The heart of this process is the concept of goal-directed
tree growth. The subchapter 'Preliminary Sketch' gives the reader a
concise and clear description of the left-to-right parsing
process. The central point may be found in the part 'The Data
Structures of the Parsing Model', because the essential goal of the
dynamic syntax is implementation in a computer which processes
language understanding in a the left-to-right fashion, thus the formal
model and data structures are the most necessary components. Here you
can find the strict and formal definitions of these notion and
structures, for example, 'language', 'basic/partial tree structures',
which will be used in the following chapters. Anyone, who wants to
continue reading this book, will have to carefully learn these formal
definitions.

Chapter 3 (The Dynamics of Tree Building): In the second chapter, the
data structures used to represent the results of parsing a natural
language string have been introduced, as well as the language defined
to describe these structures. Obviously, these descriptions and
structures are static. How to use these static and declarative
structures in dynamic parsing is main topic of the current
chapter. Here the procedural structure of the space of decorated trees
is introduced. To make the abstract process and description more
easily understood, first the authors introduce the rules that license
transitions from tree to tree by setting out three examples, step by
step. These rules license the development of a logical form
represented by a tree. There are three types of rule: introducing
requirements for appropriately annotated nodes, regulating the
incorporation of lexical information in the tree, and propagating and
compiling the information upward in a tree. It is worth noting that
this system differs from other, more familiar or traditional
systems. The new system and method defines possible transitions from
one tree to another without reference to any independent set of axioms
that constitute the grammar of the language, in other words, the
transition rules themselves incorporate the grammar. In the 3.2 part,
the parsing process above described is formally defined. According to
this model, natural languages are no longer inference systems, but
devices for creating expressions over which inference can be
defined. If you have a background of computational linguistics and
know other formalism, the summary of this chapter is very
useful. Here, the authors describe the differences and similarities
between their system and many other formalisms, for example,
Categorical Grammar, HPSG (Head-driven Phrase Structure Grammar), LFG
(Lexical Function Grammar), DRT (Discourse Representation Theory),
Minimalist Programme, and Left-Associative Grammar. In a nutshell,
chapters 2-3 define a modular system which across a left-right
sequence of words, induces a structure from which some lambda term is
compiled representing an interpretation of the string.

Chapter 4 (Linked Tree Structures): The authors give a
characterization of the process of building up interpretation for
relative clause sequences, with a preliminary indication of how a
cross-language typology for these structures might be developed and
how information may be copied from one tree structure to
another. Setting out this typology will involves surveying restrictive
and non-restrictive relatives, head-initial, head-final and
head-internal relatives. For demonstrating the cross-linguistic
validity of this method, the examples from some languages are given.

Chapter 5 (Wh questions: A General Perspective): in this chapter the
authors investigate the range of wh questions across languages in the
framework of dynamic syntax they have build in the previous
chapters. Many questions on wh problems are discussed and defined: the
semantic diversity, scopal properties of wh expressions, wh-initial vs
wh-in-situ structures, expletive wh structures. One important
difference between this approach and all others is that it completely
lacks the concept of the wh expression corresponding to an operator
binding some discrete position and variable.

Chapter 6 (Crossover Phenomena): the focus of this chapter is the
interaction between the processes involved in establishing the
interpretation of left-dislocated wh expressions and anaphoric
expressions - the phenomenon of crossover. What we can see in these
analyses of relative clauses and wh questions is that natural
typologies emerge as individual language systems which are analyzed as
making available different underspecified descriptions, with
consequent variation in the dynamics of their resolution.

Chapter 7 (Quantification Preliminaries) outlines ways in which
quantification might be reflected in this model.

Chapter 8 (Reflections on Language Design): the authors step back to
consider the general issues raised by this dynamic view for studying
the relevance of the results on general linguistic theory. On this
view, the well-formedness of a string is: if, using all its words in a
left-to-right order, it creates at least one logical form. The syntax
of natural language will thus be described as incrementally building
up structures representing the interpretation. For the readers, the
first part of this chapter provides an overall perspective of the
whole book in general language. Other subchapters are:
'Underspecification and the Formal Language Metaphor, English is not a
formal language', 'Well-formedness and Availability of
Interpretations', 'Universals and Language Variation', 'On Knowledge
of Language'. The final chapter (The Formal Framework) provides a more
explicit and formal statement of the rules and assumptions set out in
Chapter 2 and 3. The declarative and procedural part of this model is
described by Propositional Dynamic Logic (PDL). In addition to the
mentioned nine chapters, there is a 12-page bibliography and 9-page
'general index'. As a book with a rich logical notation, the authors
also add a useful 'symbol index' in the end of this book. This book
has beautiful aspects, but it is not an easy thing to attain this
result for such content with complex symbols and tree
structures. There is a small mistake in Bibliography. The authors list
the Jiang (1995) and Yiang (1995) as two different items of same PhD
thesis of Jiang Yan; the latter is the result of an erroneous
understanding of a Chinese surname.

COMMENTS

In the preface of this book, the authors say that they want to
convince their readers that the time has come to shift from the static
perspective of formalisms based on the familiar classical logics to a
more dynamic formalism where the emphasis is on the process and the
incremental development of structure. In fact, we can see such shift
from some others works, for example, Left Associative Grammar
(Hausser, 2001), Axiomatic Grammar (Milward, 1991), Dynamic Dependency
Grammar (Milward, 1994), State Transition Grammar (Tugwell, 1998). In
other words, the researchers now pay attention to the dynamic process
of language understanding. Although we have had many formal theories
and systems for natural language processing, the final goal of
language processing by computer is still a long way off. The model
proposed by the authors of this book undoubtedly is a useful
exploration for natural language processing in particular, and the
study of human intelligence in general. According to the principle of
this model, it seems a better simulation of the mechanism of human
language processing than others. Because there are essential
differences between the structures of computers and humankind, we do
not know whether we should make the systems following the mechanisms
of machines or humankind. Fortunately, many experiments and studies on
language processing have proved that language processing is a
knowledge-based mechanism. Unfortunately, we still do not clearly
know what precise meanings are, how to use this knowledge during the
procedure of language understanding, and how to structure and store
this knowledge in the computer. We have a right to reserve the
implications of such mechanism in a system, but the knowledge
processing elements is certainly necessary to any system of language
processing. In the eyes of the authors, at least, "so-called
'knowledge' of language is simply the capacity to construct
appropriate decorated structures as interpretations of stimuli of a
particular sort".

We remark that in this book the authors use IF-THEN-ELSE fashion as
conditions of lexical action (transition), it is not difficult to view
that as a knowledge-driven action. Using IF-THEN-ELSE as the method of
knowledge representation is not rare in the technique of artificial
intelligence (Expert System based on rule). Feng Zhiwei has mentioned
the usefulness of this rule's representation in natural language
processing (Feng, 1992:116-123).

In this book, there are many examples from different languages, in
other words, the model is cross-linguistically valid.

This book is very helpful and useful to anyone, who wants to know how
to simulate the capability of human language processing from the
common-sense view in a logical fashion. More precisely, it is useful
to all interested in the modeling of natural languages based on logic
in particular, language understanding and linguistic theory in
general.


REFERENCES

FENG Zhiwei (1992) Zhongwen Xinxichuli yu Hanyu yanjiu (Chinese
Information Processing and The study of Chinese). Beijing: Commercial
Press.

Hausser, R. (2001) Foundations of Computational Linguistics. The
second edition. Berlin: Springer.

Milward, D. (1991) Axiomatic Grammar, Non-Constituent Coordination and
Incremental Interpretation . PhD. Thesis, Computer Laboratory,
University of Cambridge.

Milward, D. (1994) Dynamic Dependency Grammar, Linguistics and
Philosophy 17, 561-605.

Tugwell, D. (1998). Dynamic syntax. Ph.D Dissertation. Edinburgh
University.

ABOUT THE REVIEWER

Liu Haitao is an senior engineer (=full professor in university) in
information technology and natural language processing. He has
published more than 40 articles about computational linguistics and
other branches of linguistics. He is interested in general problems
of computational linguistics and interlinguistics and their
relationship to other sciences.
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