This picks up on Bernard's point regarding Sets in RM. I appreciate that
RM does not subscribe to any mathematical set model but i wonder about
when do individuals become sets?
I'm not sure I found it but if I have two assertions in different maps where:
graham worksfor empolis gmbh
graham worksfor empolis uk
and I merge them what happens?
is it now true that
graham worksfor [empolis gmbh, empolis uk]
through merging, or are the two assertions seperate?

Exact. But if the role player x is not a set, how do
you make distinct the subject x and the set {x}? The second one is also a
subject, which is exactly the set of subjects that play the role ... So
you have a problem here, and the only consistent way I see to solve it is
to say: "a role player is always a set of subjects".