Head-driven Phrase Structure Grammar I
Head-driven Phrase Structure Grammar I
Head-driven Phrase Structure Grammar I
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Basic Idea Typed feature structure HPSG: First glance<br />
Type hierarchy: Subsumption<br />
◮ T : is a finite set of types<br />
◮ ⊑: a partial order defined on T<br />
◮ Reflexive: σ ⊑ σ<br />
◮ Antisymmetric: if σ ⊑ τ and τ ⊑ σ then σ = τ<br />
◮ Transitive: if σ ⊑ ω and ω ⊑ τ then σ ⊑ τ<br />
◮ Subsumption: For types σ, τ ∈ T , σ subsumes or is more<br />
general than or is a supertype of τ, when σ ⊑ τ.<br />
◮ τ is subsumed by or is more specific than or is a subtype of σ.<br />
Example<br />
dolphin elephant salmon<br />
aquatic-animal terrestrial-animal mammal fish<br />
animal<br />
Weiwei Sun <strong>Head</strong>-<strong>driven</strong> <strong>Phrase</strong> <strong>Structure</strong> <strong>Grammar</strong> I 18/61