[log in to unmask]" type="cite">The trouble is that <repository> is given without the '?' quantifier thus making it mandatory if any other element from sequence is present. This is confirmed by the validator: as long as there's a <repository>, anything goes. I don't think this omission of the '?' quantifier in ROMA is intentional, though.Ah, I missed that one. This indeed looks like an oversight in ROMA.No, I don't think so. My recollection is that the manuscript experts on that task force believed that a repository was required. Any of the other MSsers care to comment? (It would actually be an easier content model to maintain if repository were also optional, because then what is now a reference to a model class followed by four references to specific elements could become one reference to a specialized model class.)