Head-driven Phrase Structure Grammar I

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