protected function _checkSearchConfig( array $config )
	{
		$required = array( 'id', 'label', 'status', 'level', 'left', 'right' );

		foreach( $required as $key => $entry )
		{
			if( isset( $config[$entry] ) ) {
				unset( $required[$key] );
			}
		}

		if( count( $required ) > 0 )
		{
			$msg = 'Search config in given configuration are missing: "%1$s"';
			throw new MW_Tree_Exception( sprintf( $msg, implode( ', ', $required ) ) );
		}
	}