Reported

xsd is only rules to validate dates insert in that xml. Not really of interest to read api.
but maybe I didn't understand exactly the question or i ignore something about xml.

founder is a number id and can change, if change who is actual setted as founder.
foundDate is a number , dataunix and say when is created ally, and so cannot change.

If you provide a xml and mention the corresponding xsd file, this should validate. Technically you can ignore it, but I think it is important to fix this, because some of the other documents have optional tags and attributes – you know them through the xsd file.