protected  function _createSchema( MW_DB_Connection_Interface $conn, $adapter, $dbname )
	{
		if( empty( $adapter ) || ctype_alnum( $adapter ) === false ) {
			throw new MW_Setup_Exception( sprintf( 'Invalid database adapter "%1$s"', $adapter ) );
		}

		$classname = 'MW_Setup_DBSchema_' . ucwords( strtolower( $adapter ) );

		if( class_exists( $classname ) === false ) {
			throw new MW_Setup_Exception( sprintf( 'Database schema class "%1$s" not found', $classname ) );
		}

		return new $classname( $conn, $dbname );
	}