public function correctToJSON(){
        $returnValue = null;

        try{
            $correctResponses = $this->getCorrectResponses();
            if(count($correctResponses)){
                $returnValue = taoQTI_models_classes_Matching_VariableFactory::createJSONVariableFromQTIData(
                    $this->getIdentifier()
                    , $this->getAttributeValue('cardinality')
                    , $this->getAttributeValue('baseType')
                    , $this->correctResponses
                );
            }
        }catch(Exception $e){

        }

        return $returnValue;
    }