protected Relation parseRelation() throws XMLStreamException {
RelationData rd = new RelationData();
readCommon(rd);
Relation r = new Relation(rd.getId(), rd.getVersion());
r.setVisible(rd.isVisible());
r.load(rd);
externalIdMap.put(rd.getPrimitiveId(), r);
Collection<RelationMemberData> members = new ArrayList<>();
while (true) {
int event = parser.next();