Whether it is read · The usage · Element
The engagement
Whether opening it means anything.
The part
What it is
Time spent, interactions and whether the reader went further into the detail. Opening and closing immediately is not usage.
For most estates, opens alone are sufficient to identify the unused majority.
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.