NEG — Wha tis a root CollaborationElement?

Page 88 and 89: The text refers to a "root CollaborationElement". What is
a root CollaborationElement? Root of what?
Page 88, 4th full paragraph, 1st sentence reads: "On invocation of the
apply operation, the implementation of Collaboration executes the
verification of the principal as a registered Member of the
Collaboration..." How does the Collaboration implementation determine the
MemberKind of the caller of the apply operation and whether it is an
initiator or responder with respect to the active state? Via
CORBA::Current? This must be explained in detail.