Head-driven Phrase Structure Grammar I

Basic Idea Typed feature structure HPSG: First glance
TFS: Formal definition
Definition
A typed feature structure is defined on a finite set of features F
and a type hierarchy 〈T , ⊑〉. It is a tuple 〈Q, r, δ, θ〉, where:
◮ Q is a finite set of nodes
◮ r ∈ Q (r is the root node)
◮ δ : Q × F ↦→ Q is a partial feature value function
◮ θ : Q ↦→ T is a partial typing function
subject to the following conditions:
1. r isn’t a δ-descendant.
2. all members of Q except r are δ-descendants of r.
(*) there is no node n or path π such that δ(n, π) = n.
Weiwei Sun Head-driven Phrase Structure Grammar I 26/61