public void newValueType(String domainName, ValueType valueType) {
   if (domainName == null) {
     domainName = valueType.getFullname();
   }
   valueType.getBaseType().setDomainName(domainName);
   checkValueTypeName(domainName);
   valueTypes.put(domainName, valueType);
 }
 public static boolean isNullableType(ValueType vt) {
   String vtFullName = vt.getFullname();
   for (String nonNullableType : NON_NULLABLE_TYPES) {
     if (nonNullableType.equals(vtFullName)) {
       return false;
     }
   }
   return true;
 }