public function getRange()
    {
        $returnValue = null;
   
		if (is_null($this->range)){
			$rangeProperty = $this->getProperty(OntologyRdfs::RDFS_RANGE);
            $rangeValues = $this->getPropertyValues($rangeProperty);

            if(sizeOf($rangeValues)>0){
                $returnValue = $this->getClass($rangeValues[0]);
            }
			$this->range = $returnValue;
		}
		$returnValue = $this->range;
        return $returnValue;
    }