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 unification: Definition<br />
Definition<br />
Unification of types τ 1 , τ 2 ∈ T is an operation to compute the<br />
least upper bound of τ 1 and τ 2 . Type unification of τ 1 and τ 2 if<br />
denoted by τ 1 ⊔ τ 2 . That is,<br />
{ σ if lub(τ1 , τ<br />
τ 1 ⊔ τ 2 =<br />
2 ) = {σ}<br />
undefined otherwise<br />
dolphin elephan 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 21/61