Optional qualifier in OMR spec

[N. W. Perry]

I'm looking to clarify the use of optional qualifiers in the OMR spec.

Under Base File Naming, the requirements for the optional qualifier are:

• "[i]s a sequential number, starting with 2."
  
• "…is not mandatory and gets added only if there is more than one set that could be assigned the same <Set Number>. The first set using a given number would be understood to never contain the qualifier however numbering should start with the oldest set and some investigation should be done in existing set databases."
  

Under MPD File Structure, the requirement for the optional qualifier, both for sub-models and embedded unofficial parts, is:

•  "is a sequential number, starting with 1, added if there is more than one set that could be assigned <Set Number>."
  

This has the effect that, where the model represents the first (oldest) of multiple sets with the same number, the MPD filename would not contain the optional qualifier, but the names of its subfiles would. So, to extend the example given in the spec:

6901 - Mobile Lab.mpd (Produced in 1980)
6901-1 - Submodel1.ldr
6901-1 - Submodel2.ldr
6901-1 - part.dat
6901-2 - Space Plane.mpd (Produced in 1998)

Likewise, the example given for an embedded unofficial part is:

33956.dat would be renamed to 3345 - 33956.dat or 3345-1 - 33956.dat[color=rgba(0, 0, 0, 0.87)].[/color]

In either case, the underlying base filename would be 3345 - Set Name.mpd (because "-1" is not a valid optional qualifier for the base filename, or because there is only one set numbered 3345).

Is this the intended interpretation of the spec? Or is it intended that <Set Number>[-<Optional Qualifier>] be identical for the base filename and all subfile names (and if so, should the optional qualifier start at 1 or 2)?