The occurrence could be checked in XI after importing the message in mapping. However, in the external definition too, you may check the occurrence attribute. Just to inform you, the mandatory field does not always mean that you satisfy all business requirement related to data involved. So make sure with the business about the process requirements.
Regards,
Prateek
You must be a registered user to add a comment. If you've already registered, sign in. Otherwise, register and sign in.