The plan · The reactive space · Element
The protection
What stops it being filled in advance.
The part
What it is
A rule and someone who enforces it. Without both, the reactive space is filled by week two of every month.
The rule should specify how close to publication a reactive piece can be committed, which is what keeps the space genuinely free.
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.