UML14 — Discussion on Collaborations and Interactions is confusing

Summary: Page 86 et seq. I find the discussion on Collaborations and Interactions etc.
confusing. It seems to be inconsistent. On page 86 we have Collaboration is
at a higher level than Interaction and Collaboration is an aggregate of
Interactions. Whilst in the Notation Guide (see also Fowler and Scott,
p103-110) Interaction diagrams are at a higher abstraction level than
Collaboration diagrams (page 80 of Notation guide)

considered and declined