protected function _getLevelFromConstant( $level )
	{
		switch( $level )
		{
			case MW_Tree_Manager_Abstract::LEVEL_ONE:
				return 0;
			case MW_Tree_Manager_Abstract::LEVEL_LIST:
				return 1;
			case MW_Tree_Manager_Abstract::LEVEL_TREE:
				return 0x7FFFFFFF; // max. possible level
			default:
				throw new MW_Tree_Exception( sprintf( 'Invalid level constant "%1$d"', $level ) );
		}
	}