public Identifier asIdentifier(Vendor vendor) {
   try {
     return vendor.parseIdentifiers(asString, 1, 1)[0];
   } catch (IdentifierParseException ex) {
     return null;
   }
 }
 public static ColumnNameR2RML create(Identifier name, Vendor vendor) {
   return name == null ? null : new ColumnNameR2RML(vendor.toString(name));
 }