Issuer and assigner are not null / empty but I'm not sure that information would be available in all cases on software systems.
I would like to know opinions on relaxing the rules for those two fields and make them optional.
RM Release 1.0.3 was indeed relaxing those attributes requirements, but invariants are still there. I suggest to correct them (documentation) in 1.0.4
Yep, we made an error in the UML model and didnt get rid of the invariant constraints. We'll correct this as a publishing error.