Now is the time to start reading Ginzburg and Sag 2000, Chapter 2. You can skim the first part about the lexicon. Parts of speech. Verbs and complementizers. Realis SOAs and Irrealis SOAs.
Clauses ground the message recursion.
The Schemata of HPSG 2 become nonmaximal types. The finite VP construction. Do Without Transformations or Optimization. Manuscript, Stanford University. Negation without Head Movement.