Where they are · The cost to reach · Element
The price
What it costs to reach a thousand of them here.
The part
What it is
Comparable across places only when the relevance is factored in: a cheap place where a twentieth of the audience is yours is not cheap.
Effective cost per relevant contact is the figure that makes places comparable.
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.