So `minOccurs="1" maxOccurs="1"` is the default value. I've cleaned up the file in this regard. However, I couldn't get a file to break with this, probably because we've got these wrapped in a `choice`. Thus, while I can specify that only one `read-preference` element can be provided, there can be multiple `choice` elements, of which each can be a `read-preference` element. I'm not sure how to solve this in XSD land.