public function generateIdentifier( $id, $attributes = null )
    {
        $identifier = strtolower( $this->backendName )
            . $this->properties['location']
            . $id 
            . (
                ( $attributes !== null && !empty( $attributes ) ) 
                ? md5( serialize( $attributes ) ) 
                : ''
        );
        return urlencode( $identifier );
    }