UML14 — Collaboration showing instances

Summary: If "an Interaction specifies messages sent between instances" (pg. 83)
where
are the instances on the diagram on page 81?
I think a clear distinction between the meta-levels should be made. If
Collaborations show ClassifierRoles and AssociationRoles (see fig. 15
pg.
81), the text should not imply that they show Instances and Links. The
concepts are distinct, since they are modeled through two different
classes
in the metamodel.

Considered and declined.