protected function unmarshallChildrenKnown(DOMElement $element, QtiComponentCollection $children)
    {
        if (($min = $this->getDOMElementAttributeAs($element, 'min')) !== null) {

            if (Format::isInteger($min)) {
                $min = intval($min);
            }

            if (($max = $this->getDOMElementAttributeAs($element, 'max')) !== null) {

                if (Format::isInteger($max)) {
                    $max = intval($max);
                }

                $object = new AnyN($children, $min, $max);

                return $object;
            } else {
                $msg = "The mandatory attribute 'max' is missing from element '" . $element->localName . "'.";
                throw new UnmarshallingException($msg, $element);
            }
        } else {
            $msg = "The mandatory attribute 'min' is missing from element '" . $element->localName . "'.";
            throw new UnmarshallingException($msg, $element);
        }
    }