Another Group - Role Distinction?

Is it the case that groups propagate "up" whereas roles propagate "down" for
security purposes?

For example:

humans is a subgroup primates
X is a member of humans
----------------
X is a member of primates = True

humans is a subgroup primates
X is a member of primates
-----------------
X is a member of humans = Unknown

junior auditor is a child-role of senior auditor
X can play role junior auditor
-----------------
X can play role senior auditor = Unknown

junior auditor is a child-role of senior auditor
X can play role senior auditor
-----------------
X can play role junior auditor = True



Simon Y. Blackwell 
CTO 
Psoom, Inc. 
Voice & Fax: 415-762-9787