lect2-regex - R e g u la r L a n g u a g e s L e c tu re 2...

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Andrew McCallum, UMass Amherst, including material from Chris Manning and Jason Eisner Regular Languages Lecture #2 Introduction to Natural Language Processing CMPSCI 585, Fall 2007 University of Massachusetts Amherst Andrew McCallum
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Andrew McCallum, UMass Amherst, including material from Chris Manning and Jason Eisner Today’s Main Points • A brief history • What are regular languages, finite state automata and regular expressions? • Writing regular expressions (in Python) • Examples on several large natural language corpora • Finite-state transducers, and morphology • Homework assignment #1
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Andrew McCallum, UMass Amherst, including material from Chris Manning and Jason Eisner Some brief history: 1950s • Early CL on machines less powerful than pocket calculators. • Foundational work on automata, formal languages, probabilities and information theory. • First speech systems (Davis et al, Bell Labs). • MT heavily funded by military, but basically just word substitution programs. • Little understanding of natural language syntax, semantics, pragmatics.
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Andrew McCallum, UMass Amherst, including material from Chris Manning and Jason Eisner Some brief history: 1960s • Alvey report (1966) ends funding for MT in America - the lack of real results realized • ELIZA (MIT): Fraudulent NLP in a simple pattern matcher psychotherapist – It’s true, I am unhappy. Do you think coming here will make you not to be unhappy? – I need some help; that much is certain. What would it mean to you if you got some help? – Perhaps I could earn to get along with my mother. Tell me more about your family. • Early corpora: Brown Corpus (Kudera and Francis)
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Andrew McCallum, UMass Amherst, including material from Chris Manning and Jason Eisner Some brief history: 1970s • Winograd’s SHRDLU (1971): existence proof of NLP (in tangled LISP code). • Could interpret questions, statements commands. – Which cube is sitting on the table? The large green one which supports the red pyramid. – Is there a large block behind the pyramid? Yes, three of them. A large red one, a large green cube, and the blue one. – Put a small one onto the green cube with supports a pyramid. OK.
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Andrew McCallum, UMass Amherst, including material from Chris Manning and Jason Eisner Some brief history: 1980s • Procedural --> Declarative (including logic programming) • Separation of processing (parser) from description of linguistic knowledge. • Representations of meaning: procedural semantics (SHRDLU), semantic nets (Schank), logic (perceived as answer; finally applicable to real languages (Montague) • Perceived need for KR (Lenat and Cyc) • Working MT in limited domains (METEO)
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Andrew McCallum, UMass Amherst, including material from Chris Manning and Jason Eisner Some brief history: 1990s • Resurgence of finite-state methods for NLP: in practice they are incredibly effective. • Speech recognition becomes widely usable.
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lect2-regex - R e g u la r L a n g u a g e s L e c tu re 2...

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