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Unformatted text preview: Speech and Language Processing An Introduction to Natural Language Processing, Computational Linguistics, and Speech Recognition Second Edition Daniel Jurafsky Stanford University James H. Martin University of Colorado at Boulder Upper Saddle River, New Jersey 07458 Chapter 1 Introduction Dave Bowman: Open the pod bay doors, HAL. HAL: Im sorry Dave, Im afraid I cant do that. Stanley Kubrick and Arthur C. Clarke, screenplay of 2001: A Space Odyssey The idea of giving computers the ability to process human language is as old as the idea of computers themselves. This book is about the implementation and implications of that exciting idea. We introduce a vibrant interdisciplinary f eld with many names cor- responding to its many facets, names like speech and language processing , human language technology , natural language processing , computational linguistics , and speech recognition and synthesis . The goal of this new f eld is to get computers to perform useful tasks involving human language, tasks like enabling human-machine communication, improving human-human communication, or simply doing useful pro- cessing of text or speech. One example of a useful such task is a conversational agent . The HAL 9000 com- Conversational agent puter in Stanley Kubricks f lm 2001: A Space Odyssey is one of the most recognizable characters in 20th century cinema. HAL is an arti f cial agent capable of such advanced language behavior as speaking and understanding English, and at a crucial moment in the plot, even reading lips. It is now clear that HALs creator, Arthur C. Clarke, was a little optimistic in predicting when an arti f cial agent such as HAL would be avail- able. 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 humans in natural language conversational agents or dialogue systems . In this text we study the vari- Dialogue system ous components that make up modern conversational agents, including language input ( automatic speech recognition and natural language understanding ) and language output (dialogue and response planning and speech synthesis ). Lets turn to another useful language-related task, that of making available to non- English-speaking readers the vast amount of scienti f c information on the Web in En- glish. Or translating for English speakers the hundreds of millions of Web pages written in other languages like Chinese. The goal of machine translation is to automatically Machine translation translate a document from one language to another. We introduce the algorithms and mathematical tools needed to understand how modern machine translation works. Ma- chine translation is far from a solved problem; we cover the algorithms currently used in the f eld, as well as important component tasks....
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- Fall '08
- 2001: A Space Odyssey