I can't find , but only in version 1.0.1? Have I overlooked something?
From my point of view, however, it is more important that the allele-assignment is minOuccurs = "1". I would therefore suggest the following for the next version:
Also, I would suggest omitting as it makes the creation code more complex without any benefit in reading the data.
I believe quantity=1 is correct, but the description (qty: 1 or more) is inconsistent.
A minor fix if we make a 1.0.2 xsd.