The decision

What was decided at the checkpoint.

The part

What it is

Three outcomes are worth distinguishing: continue as planned, continue with changes, and stop. Collapsing the middle one into the first hides most of what happens.

The date matters because it establishes what was known at the time.

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.