@Override
  public void readExternal(Element element) throws InvalidDataException {
    boolean dataFound = false;
    for (Element item : element.getChildren(ITEM)) {
      if (!dataFound) {
        clear(); // remove default values
        dataFound = true;
      }
      String value = item.getAttributeValue(VALUE);
      add(value == null ? null : StringUtil.unescapeXmlEntities(value));
    }
  }
@Override
  public void readExternal(Element element)