What it rules out · The exclusions · Element
The boundary cases
The things that are almost excluded.
The part
What it is
Every exclusion has near neighbours that are technically allowed, and those are where the argument actually happens.
Naming a few in advance turns a future dispute into a precedent.
The smallest level
The attributes it carries
Each attribute is one of the framework’s shared types. What a date is, and how it is written, is defined once for the whole model — the note here says what it means in this particular place.