Avoid “shall” in a definition (here embedded in a table). “Shall” is reserved in ISO for requirements.
Question for HMMG? How to deal with requirements that are caused by constraints in the data models? Should they be called out as requirements of the standard, or left implicit in a general requirement to adhere to the model.
Either call this out as an identified requirement of the standard
Or add it as an OCL “unique” constraint on the model