public static function getInstance($name)
  {
    $key = self::_instanceKey($name);
    if (!isset(self::$_instances[$key])) {

      $dataSource = self::getDataAdapter();
      if (is_null($dataSource)) {
        $data = array();
      } else {
        $data = $dataSource->load($key);
      }
      
      $config = new self($data);
      /* @var $config Config */
      $config->_root = $config;
      $config->_key = $key;

      self::$_instances[$key] = $config;
    }
    return self::$_instances[$key];
  }