parid0213 | Tue, 25 Feb 2003 17:04:28
The role types that participate in any given assertion instance must always constitute a set, i.e., within any single assertion, no two role types can be the same. Each role type has a maximum of one role player.
covered in rules for assertions. Should be role has only one role
player. Class characteristics should be asserted about the role by a
separate assertion.