Phrase structure (constituency) grammars

Take the part-whole relationship as fundamental.
A sentence analysis consist of phrases, which may consist of phrases or words.
A grammar takes the form of a set of context-free rewrite rules.
Variants
- Probabilistic context-free grammars
- Categories replaced with feature structures, for example, in Head-Driven Phrase Structure Grammar

Dependency grammars

Take the head-dependent relationship as fundamental.
A sentence analysis consists of a set of labeled head-dependent relationships between words (there are no phrases).
A grammar takes the form of a lexicon with word-specific constraints about valency, order, and agreement

Parsing
- Dynamic programming, chart parsing
- Constructive and eliminative parsing
- Deterministic parsing
- The fundamental problem: ambiguity (lexical, syntactic)
Generation
- Usually starts with semantic (and/or pragmatic) input
- Incremental and batch generation
- Lexically-driven and grammar-driven generation
- Fundamental problems
  - The mismatch between semantic/pragmatic and surface structure
  - Deciding what to mention
  - Referring expressions