if (SchemaNames.KEYREF.equals(elementName)) {
String refer = atts.getValue("refer");
if (refer == null) {
error("The 'refer' attribute for keyref must exist.");
}
_identityConstraint = new KeyRef(name, refer);
}
//-- unique
else if (SchemaNames.UNIQUE.equals(elementName)) {
_identityConstraint = new Unique(name);
}