context PolicyActivity
inv: self.participant->size()=1 and 
self.participant->forAll(part : POCDMT000040Participant2 | 	
		part.participantRole.oclIsUndefined() or
		(not part.participantRole.nullFlavor.oclIsUndefined()) or
		(
			not part.participantRole.code.oclIsUndefined() and 
			part.participantRole.code.nullFlavor.oclIsUndefined()
			)
)