public function indexOf( common_Object $resource)
    {
        $returnValue = null;

        
        $returnValue = -1;
        foreach($this->sequence as $index => $_resource){
        	if ($_resource instanceof  core_kernel_classes_Resource){
				if($resource->equals($_resource)){
					return $index;
				}
        	}
		}
        

        return $returnValue;
    }