Unification Grammar

AKA: Constraing-based Grammar.
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- Is more general than a Context Free Phrase-Structure Grammar.
- It can "describe linguistic objects by using feature structures consisting of features and associated values that encode several levels of linguistic information (e.g. morphological, syntactic, semantic)."

See: Grammar.

References

(Kakkonen, 2007) ⇒ Tuomo Kakkonen. (2007). “Framework and Resources for Natural Language Evaluation." Academic Dissertation. University of Joensuu.
- Unification grammars (UGs), which are also known as constraint-based grammars, were specifically developed to overcome the problems that CFPSGs encounter when representing fine-grained grammatical information such as agreement and subcategorization (Carpenter 1989). This section introduces three of the best-known UGs, namely, Generalized Phrase Structure Grammar (GPSG) (Gazdar et al. 1985). “Head-driven Phrase Structure Grammar (HPSG) (Pollard & Sag 1987, 1994) and Lexical Functional Grammar (LFG) (Kaplan & Bresnan 1982). UGs are able to model more complex linguistic phenomena than CFGs. These formalisms describe linguistic objects by using feature structures consisting of features and associated values that encode several levels of linguistic information (e.g. morphological, syntactic, semantic) in a uniform way.
- Definition 3-12. Head-driven Phrase Structure Grammar (Pollard & Sag 1987).
  - A Head-driven Phrase Structure Grammar is defined as P1 Ù ...Ù Pn+m Ù (L1 Ú ...Ú Lp Ú R1 Ú ...Ú Rq ) where P1…Pn are universal principles common to all languages, Pn+1…Pn+m are language-specific principles, L1…Lp are the lexical signs of a language, and R1…Rq are its grammar rules.