protected function marshall(QtiComponent $component)
    {
        $element = parent::marshall($component);
        $this->setDOMElementAttribute($element, 'outcomeIdentifier', $component->getOutcomeIdentifier());

        $weightIdentifier = $component->getWeightIdentifier();
        if (!empty($weightIdentifier)) {
            $this->setDOMElementAttribute($element, 'weightIdentifier', $weightIdentifier);
        }

        return $element;
    }