Head-driven Phrase Structure Grammar I

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Basic Idea Typed feature structure HPSG: First glance Type constraints and appropriate features: Formal stuff (skip) Constraint function C : T ↦→ FS obeys the following conditions: 1. Type For a given type t, if C(t) is the feature structure 〈Q, r, δ, θ〉 then θ(r) = t. 2. Monotonicity Given type t 1 and t 2 , if t 1 ⊑ t 2 then C(t 1 ) ⊑ C(t 2 ). 3. Compatibility of constraints For all q ∈ Q the feature structure C(θ(q)) ⊑ F ′ = 〈Q ′ , q, δ, θ〉 and Feat(q) = Appfeat(θ(q)) 4. Maximal introduction of features For every feature f ∈ Feat there is a unique type t such that f ∈ Appfeat(t) and there is no type s such that s ⊏ t and f ∈ Appfeat(s). Weiwei Sun Head-driven Phrase Structure Grammar I 49/61
Basic Idea Typed feature structure HPSG: First glance Type inference: Making a TFS well-formed ◮ Apply all type constraints to convert a TFS into a well-formed TFS. ◮ Determine most general well-formed TFS subsumed by the input TFS; ◮ Specialize all types so that all features are appropriate: [ ] [ ] head pos head pos → args *list* args *list* ⊥ phrase ◮ Expand all nodes with the type constraint of the type of that node: [ ] head pos → args *list* phrase ⎡ head args ⎢ ⎣spr comps phrase ⎤ pos *list* *list* ⎥ ⎦ *list* Weiwei Sun Head-driven Phrase Structure Grammar I 50/61
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Head-driven Phrase Structure Grammar I

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