Scope · The boundary · Element
The in-scope edge
The furthest thing that is still in scope.
The part
What it is
Defining the edge from the inside is more useful than listing exclusions, because it gives a positive test rather than a growing list of refusals.
It also makes the boundary discussable when a genuinely new opportunity appears.
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.