DRAFT - Speech and Language Processing (2nd ed).pdf

Speech and Language Processing: An introduction to natural language processing,
computational linguistics, and speech recognition. Daniel Jurafsky & James H. Martin.
Copyright
c 2006, All rights reserved. Draft of June 25, 2007. Do not cite without
permission.
1 INTRODUCTION
Dave Bowman: Open the pod bay doors, HAL.
HAL: I’m sorry Dave, I’m afraid I can’t do that.
Stanley Kubrick and Arthur C. Clarke,
screenplay of 2001: A Space Odyssey
This book is about a new interdisciplinary field variously puter speech
and language processing or human language technology or natural language pro-
cessing putational linguistics. The goal of this new field is to puters
to perform useful tasks involving human language, tasks like enabling human-machine
communication, improving human-munication, or simply doing useful pro-
cessing of text or speech.
CONVERSATIONAL
AGENT One example of a useful such task is a conversational agent. The HAL -
puter in Stanley Kubrick’s film 2001: A Space Odyssey is one of the most recognizable
characters in twentieth-century cinema. HAL is an artificial agent capable of such ad-
vanced language-processing behavior as speaking and understanding English, and at a
crucial moment in the plot, even reading lips. It is now clear that HAL’s creator Arthur
C. Clarke was a little optimistic in predicting when an artificial agent such as HAL
would be available. But just how far off was he? What would it take to create at least
the language-related parts of HAL? We call programs like HAL that converse with hu-
CONVERSATIONAL
AGENTS mans via natural language conversational agents or dialogue systems. In this text we
DIALOGUE SYSTEMS study the ponents that make up modern conversational agents, including
language input (automatic speech recognition and natural language understand-
ing) and language output (natural language generation and speech synthesis).
Let’s turn to another useful language-related task, that of m