protected function unmarshallChildrenKnown(DOMElement $element, QtiComponentCollection $children)
    {
        $object = new Substring($children);

        if (($caseSensitive = $this->getDOMElementAttributeAs($element, 'caseSensitive', 'boolean')) !== null) {
            $object->setCaseSensitive($caseSensitive);
        }

        return $object;
    }