12 — Projection: what the model is shown, and why not the AST

After this lesson you will be able to name the three things a model sees — schema, catalogue, outline — and say what each is a projection of; give the argument for why the reply schema is hand-written rather than derived; explain what a compiled-grammar budget is, why it exists, and why depth is not what consumes it; say what the catalogue projects and what it deliberately leaves out; and give the one property every projection in this system shares.

Prerequisites: 01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11.

Lesson 11 said what does not cross the seam. This one says what does, and how it has to be reshaped before it can.