Sizing · The three sizes · Element
The total
Everything spent on this need, everywhere, by everyone.
The part
What it is
Useful for judging whether a category is worth being in at all, and useless for anything more specific.
It should be stated with its boundaries, since a total market figure without a definition can be made almost any size.
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.