Deliverability · The cost to keep · Element
The marginal cost
What it costs each time the promise is actually invoked.
The part
What it is
Expedited shipping, a refund, an out-of-hours response, a replacement. This scales with volume and with how often customers rely on the promise.
A promise cheap at current volume and expensive at three times the volume is worth knowing about before the volume arrives.
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.