Sourcing · The supplier list · Element
The terms
The commercial arrangement with each supplier.
The part
What it is
Price, minimum order, lead time, payment terms and notice. All five affect the real cost and only the first is usually compared.
Terms agreed years ago and never revisited are common, and revisiting them is one of the cheaper improvements available.
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.