Re: mandatory or not attributes series [unordered at most once each]

Many thanks for this help.
I understand that such constraints are mostly part of the business
process.

Following, anyway, on filling "as is" an objects tree, I was thinking
to add exceptions to setters (for example "if this.att != null throw
new someting() else this.att = param;") and a completeness validation
method to call before ending to treat the objects ; there could be
thrown another exception.

.