public function validate(&$msg = null)
    {
        if (!isset($this->_name) && !isset($this->_value) && !isset($this->_file)) {
            return false;
        } elseif (isset($this->_file) && (isset($this->_name) || isset($this->_value))) {
            return false;
        } elseif ((isset($this->_name) && !isset($this->_value)) || (!isset($this->_name) && isset($this->_value))) {
            return false;
        } else {
            return true;
        }
    }