public function getUniquePropertyValue( core_kernel_classes_Property $property)
    {
        $returnValue = null;

        $collection = $this->getPropertyValuesCollection($property);

        if($collection->isEmpty()){
        	throw new core_kernel_classes_EmptyProperty($this, $property);
        }
        if($collection->count() == 1 ) {
            $returnValue= $collection->get(0);
        }
        else {
            throw new core_kernel_classes_MultiplePropertyValuesException($this,$property);
        }
        return $returnValue;
    }