public function toNQuads()
    {
        $string = '"'.$this->encodeStringLitralForNQuads($this->getValue()).'"';

        if ($this->getLanguage() !== null) {
            $string .= '@'.$this->getLanguage();
        } elseif ($this->getDatatype() !== null) {
            $string .= '^^<'.$this->getDatatype().'>';
        }

        return $string;
    }