| Preface
From July to December 1997, the
Isaac Newton Institute for Mathematical Sciences in Cambridge was host
to a major international programme entitled
Neural Networks and Machine Learning. Many of the world's leading
researchers in the field participated for periods ranging from a few weeks
up to six months, and numerous younger scientists also benefited from a
variety of conferences and workshops held throughout the programme. The
Newton Institute's purpose-designed building provided a superb research
environment, as well as an excellent venue for workshops.
The first workshop of the six month programme was a two-week NATO Advanced
Study Institute on
Generalization in Neural Networks and Machine Learning. This was heavily
over-subscribed and attendance
was limited to around 90 by the capacity of the Institute as well as by the
desire to maintain an informal, interactive atmosphere. The topic of
generalization was chosen as a focal point for the workshop and provided a
common theme running through many of the presentations. This book resulted
directly from the NATO ASI, and many of the
chapters have a significant tutorial component, reflecting the instructional
aims of the workshop.
Part 1 of the book, Statistical Foundations, deals with statistical
principles and theoretical analyses which underpin current research in
neural networks and machine learning, as well as with techniques for the
assessing the performance of pattern recognition systems. The first chapter,
by Ripley, reviews several approaches to the assessment of
generalization performance from both theoretical and practical viewpoints.
Breiman then discusses the decomposition of the sum-of-squares error
into bias and variance components, and uses simple examples to illustrate
the insight which this decomposition can provide into the problem of
generalization and model complexity optimization. Next Sontag
introduces the Vapnik Chervonenkis (VC) dimension, a measure of the capacity
of a class of functions, and shows how this quantity can be computed in the
context of binary classification problems for various neural network models.
Buhmann and Tishby then apply computational learning theory to
the analysis of clustering algorithms, leading to a criterion for
determining cluster splits. The first part of the book is concluded by
Neal who discusses the empirical assessment of learning algorithms
through the framework of the
DELVE project, and illustrates this framework with an application to the
technique of automatic relevance determination.
Part 2 of the book, Algorithms and Architectures, surveys a variety
of current approaches to pattern recognition. MacKay gives an
introductory tutorial on the increasingly popular formalism of Gaussian
processes, discussing relations to earlier techniques, the choice and
adaptation of the covariance function, and applications to regression and
classification. Zhu, Williams, Rohwer and Morciniec
then present an analysis of Gaussian process regression, showing how the
optimal finite-dimensional model under a Gaussian process prior can be
expressed in terms of an infinite-dimensional principal component
decomposition. The next two chapters deal with variational techniques.
Jaakkola and Jordan introduce the framework of variational
methods for approximate inference in dense graphical
models, illustrating the technique using a medical diagnostic database.
Variational methods are then applied to the problem of learning in neural
networks by Barber and Bishop, who demonstrate a tractable
solution for general Gaussian approximations to the posterior distribution
over parameters. Vapnik then introduces the support vector technique
for regression and classification and for solving linear operator equations,
demonstrating that good results can be obtained using finite data sets in
spaces of very high dimensionality. Finally, a very different viewpoint is
adopted by Baum who discusses an economic model of intelligence in
which interacting agents partition and solve complex problems.
This book owes much to the lecturers at the NATO ASI, and I would like to
thank them for their contributions to the workshop as well as for making the
additional effort needed to prepare this volume. I would also like to thank
Joachim Buhmann, Geoffrey Hinton and Michael Jordan and for their help in
organizing the NATO ASI, as well as David Haussler, Geoffrey Hinton, Mahesan
Niranjan and Leslie Valiant for their assistance in running the overall six
month Newton Institute programme.
I am also grateful to Tim Perkins from the Department of Applied Mathematics
and Theoretical Physics at Cambridge for his contributions to the
typesetting of this book in LaTeX.
Finally, I would like to express my sincere thanks to the staff of the Isaac
Newton Institute, for their energy, enthusiasm and support throughout the
six month programme.
Christopher M. Bishop
August 1998
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