public function toQTI()
    {
        $returnValue = (string) '';

        
		$returnValue = '<responseCondition>
		    <responseIf>
	            <isNull>
	                <variable identifier="'.$this->getResponse()->getIdentifier().'" />
	            </isNull>
		        <setOutcomeValue identifier="'.$this->getOutcome()->getIdentifier().'">
		        	<baseValue baseType="'.$this->getOutcome()->getAttributeValue('baseType').'">0</baseValue>
		        </setOutcomeValue>
		    </responseIf>
		</responseCondition>';
        

        return (string) $returnValue;
    }
public function toQTI()
    {
        $returnValue = (string) '';

        
		$returnValue = '<responseCondition>
		    <responseIf>
	            <isNull>
	                <variable identifier="'.$this->getResponse()->getIdentifier().'" />
	            </isNull>
		        <setOutcomeValue identifier="'.$this->getOutcome()->getIdentifier().'">
		        	<baseValue baseType="'.$this->getOutcome()->getAttributeValue('baseType').'">0</baseValue>
		        </setOutcomeValue>
		    </responseIf>
		</responseCondition>';
        

        return (string) $returnValue;
    }
public function toQTI ( ) { $ returnValue = ( string ) '' ; $ returnValue = '<responseCondition>
		    <responseIf>
	            <isNull>
	                <variable identifier="' . $ this -> getResponse ( ) -> getIdentifier ( ) . '" />
	            </isNull>
		        <setOutcomeValue identifier="' . $ this -> getOutcome ( ) -> getIdentifier ( ) . '">
		        	<baseValue baseType="' . $ this -> getOutcome ( ) -> getAttributeValue ( 'baseType' ) . '">0</baseValue>
		        </setOutcomeValue>
		    </responseIf>
		</responseCondition>' ; return ( string ) $ returnValue ; }
although no ResponseRules are nescessary to have no responseProcessing,
add some rules to associate the interaction response with a sepcific

@access public
@author Joel Bout, <joel.bout@tudor.lu>
@return string
although no ResponseRules are nescessary to have no responseProcessing add some rules to associate the interaction response with a sepcific