(*) n u d : new / updated / deleted since previous version.

(*bis) u : updated : this can be a codelist-version incrementing.
  Note that in many, not to say all such cases, the user-community does not await such next release to implement/activate such new codelist-values.
  The reasoning is that such added value does not affect the current data-structures and hence is considered easely implementable.
  Such reasoning tends to forget how given new codelist-values might not simply affect the data, but also affect the process, which might be more of a problem...

(**) Usage: The indications Mandatory / Conditional / Optional are to be understood in respect of the actual level of the Data element:
  example given; some party data-set as a whole can be optional, while, if present, the party's name within that party data-set can be mandatory.

Remark: in UN/Edifact, "Mandatory / Conditional" are notions used within the standard.
  And within edi-guides (a refinement of a standard) the "Conditional" can become "Required / Optional / Dependent / Advised / Not used".
  Ideally we should implement the same ideas.