Context Free Phrase-Structure Grammar

A Context Free Phrase-Structure Grammar is a Context Free Grammar that can be used as a Natural Language Grammar.

• AKA: CFPSG.
• Context:
  • It can be a Probabilistic Context Free Grammar.
  • It can be a Lexicalized Context Free Phrase-Structure Grammar.
  • It can be Modeled with four components, G = (N,∑,P,S), where:
    • 1. N, the non-terminal vocabulary, is a finite set of nonterminal symbols. A set of symbols disjoint from ∑.
    • 2. ∑, the terminal vocabulary, is a finite set of terminal symbols ; ∑ ∩ N = {}. That is, the words of the language being defined.
    • 3. P = {a -> b|a∈N,b∈(Σ∪N)*} is a finite set of production rules, where a is a non-terminal and b is a sequence of one or more symbols from T \cup V.
    • 4. S ∈ N is a distinguished symbol called the sentence start symbol.
• Example(s):
  • S → NP VP; NP → NN; NN->I; VP->V
• See: Natural Language Syntactic Theory, Unification Grammar, Phrase-Structure Grammar.

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References

• (Kakkonen, 2007) ⇒ Tuomo Kakkonen. (2007). “Framework and Resources for Natural Language Evaluation." Academic Dissertation. University of Joensuu.
  • A context-free phrase structure grammar is a 4-tuple G = (N,∑,P,S), where
    • 1. N is a finite set of nonterminal symbols.
    • 2. ∑ is a finite set of terminal symbols ; ∑ ∩ N = {}.
    • 3. P = {a -> b|a∈N,b∈(Σ∪N)*} is a finite set of production rules.
    • 4. S ∈ N is a distinguished symbol called the sentence symbol.

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