Head-driven Phrase Structure Grammar I

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Basic Idea Typed feature structure HPSG: First glance TFS subsumption: Informal idea Subsumption between feature structures: ◮ A less specific (more abstract) feature structure subsumes an equally or more specific one. The subsumption symbol: ⊑. Example [ [ ] ⎡ ⎤ ◮ number PL] ⊑ number PL ⊑ number PL ⎢ ⎥ person 3 ⎣person 3 ⎦ phon dog [ ] [ ] ◮ number PL ¬ ⊑ number PL person 3 [ ] [ ] ◮ number PL ¬ ⊑ number SG ] ◮ [] ⊑ [number SG Weiwei Sun Head-driven Phrase Structure Grammar I 31/61
Basic Idea Typed feature structure HPSG: First glance TFS subsumption: Formal definition ◮ π ≡ F π ′ : feature structure F contains path equivalence or reentrancy between the paths π and π ′ Definition ◮ δ(r, π) = δ(r, π ′ ) where r is the root node of F. F subsumes F ′ , written F ⊑ F ′ , if and only if: ◮ π ≡ F π ′ implies π ≡ F ′ π ′ ◮ θ(δ(r, π)) = σ implies θ(δ(r ′ , π)) = σ ′ and σ ⊑ σ ′ . In other words, feature structure F subsumes feature structure F ′ (F ⊑ F ′ ) iff: 1. if path π is defined in F then π is also defined in F ′ and the type of the value of π in F is a supertype or equal to the type of the value of π in F ′ , and 2. all paths that are reentrant in F are also reentrant in F ′ . Weiwei Sun Head-driven Phrase Structure Grammar I 32/61
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Head-driven Phrase Structure Grammar I

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