The observed life

How long the piece actually stayed in use.

The part

What it is

Measured months after publication rather than in the first week, since the first week measures promotion and not usefulness.

A topical piece still being used a year later is evidence about the subject, not luck. It usually points at a pillar.

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.

Still used for
How long the piece continued to be used.
Duration shared type
Use after six months
What is still happening once promotion has stopped.
Measure shared type
Published
When it went out, so the measure has a baseline.
Date shared type