The related design is under http://directory.fedoraproject.org/wiki/Creation_of_an_explicit_scoping_for_the_roles_%28ticket_208%29
It implements a RFE logged under https://bugzilla.redhat.com/show_bug.cgi?id=523783

https://fedorahosted.org/389/ticket/208

https://fedorahosted.org/389/attachment/ticket/208/0001-Ticket-208-RFE-Roles-with-explicit-scoping-in-RHDS.2.patch