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WAES3303: NLP

WAES3303: NLP. rmana@um.edu.my. GRAMMAR. In constructing a grammar for a language , we are interested in: Generality : the range of sentences the grammar analyzes correctly Selectivity : the range of non-sentences it identifies as problematic

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WAES3303: NLP

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  1. WAES3303: NLP rmana@um.edu.my

  2. GRAMMAR • In constructing a grammar for a language, we are interested in: • Generality: the range of sentences the grammar analyzes correctly • Selectivity: the range of non-sentences it identifies as problematic • Understandability: The simplicity of the grammar itself * Retain its simplicity & generality as it is extended

  3. Characteristics • Pay attention to the way sentence is divided into its subparts (constituent). • Make the solutions generalizable as you can. • Test (when constructing a group of words forms a particular constituent): • If the proposed constituent does not conjoin in some sentence with constituent of the same class, it is probably incorrect • Inserting the proposed constituent into another sentences that take the same category of constituent

  4. Generative Capacity • Grammatical formalisms based on rewrite rules can be compared according to their generative capacity(GC). • GC is the range of languages that each formalism can describe. • Formal language allow a precise mathematical characterization (vs. Natural Language)

  5. GC cont. • Regular Grammar: a grammar in which the RHS of every rule consists one terminal symbol possibly followed by one nonterminal. • CFG • CSG • Type 0 • Hierarchy of Languages: Chomsky Hierarchy (1956)

  6. Parsing • Parsing as Search Procedure • Top-Down • Bottom-Up • A Bottom-Up Chart Parser • Transition Network • Recursive Transition Network (RTN) • Top-Down Chart Parsing • Augmented Transition Network (Parsing with Feature)

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