public function getExpression()
    {
        $returnValue = null;

        
		common_Logger::i('Evaluating rule '.$this->getLabel().'('.$this->getUri().')', array('Generis Rule'));
         if(empty($this->expression)){
         	$property = new core_kernel_classes_Property(RulesRdf::PROPERTY_RULE_IF);
         	$this->expression = new core_kernel_rules_Expression($this->getUniquePropertyValue($property)->getUri() ,__METHOD__);
        }
        $returnValue = $this->expression;
        

        return $returnValue;
    }