Horizon and measures · The horizon · Element
The movement
Whether the horizon has been moved, and why.
The part
What it is
A horizon that has moved twice has stopped functioning as a deadline. The record is what makes that visible before the third move.
Distinguishing a moved date from a missed one matters, because they call for different responses.
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.