Ch6-Formal Grammars of English

Ch6-Formal Grammars of English - Search and Decoding in...

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Unformatted text preview: Search and Decoding in Speech Recognition Formal Grammars of English February 13, 2012 Veton Kpuska 2 Formal Grammars of English Oldest Grammar written 2000 years ago by Panini for Sanskrit language. Geoff Pullum noted in a recent talk that almost everything most educated Americans believe about English grammar is wrong. February 13, 2012 Veton Kpuska 3 Formal Grammars of English Syntax: Syntaxis Old Greek means setting out together or arrangement it refers to the way the words are arranged together. Syntactic notions discussed previously: Regular Languages Computation of Probabilities of those representations of Regular Languages. Introduction of sophisticated notions of syntax and grammar that go beyond these simpler notions: Constituency Grammatical relations Subcategorization and dependency. February 13, 2012 Veton Kpuska 4 Constituency Groups of words may behave as a single unit or phrase called constituent. Example: noun phrase often acting as a unit Single words: She, or Michael Phrases: The house Russian Hill, and A well-weathered three-story structure. Context-free grammars a formalism that will allow us to model these constituency facts. February 13, 2012 Veton Kpuska 5 Grammatical Relations Formalization of ideas from traditional grammar such as SUBJECTS and OBJECTS, and other related notions. In the following sentence the noun phrase She is the SUBJECT and a mammoth breakfast is the OBJECT: She ate a mammoth breakfast. February 13, 2012 Veton Kpuska 6 Subcategorization and Dependency Relations Subcategorization and dependency relations refer to certain kinds of relations between words and phrases. For example the verb want can be followed by an infinitive, as in: I want to fly to Detroit , or a noun phrase, as in I want a flight to Detroit . But the verb find cannot be followed by an infinitive *I found to fly to Dallas . These are called facts about the subcategorization of the verb. February 13, 2012 Veton Kpuska 7 Context-Free-Grammars As well see, none of the syntactic mechanisms that weve discussed up until now can easily capture such phenomena. They can be modeled much more naturally by grammars that are based on context-free grammars. Context-free grammars are thus the backbone of many formal models of the syntax of natural language (and, for that matter, of computer languages). As such they are integral to many computational applications including grammar checking, semantic interpretation, dialogue understanding, and machine translation. February 13, 2012...
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Ch6-Formal Grammars of English - Search and Decoding in...

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