The ETL meta data is data about the ETL process. The ETL meta data is modifiable. When a customer needs to make an alteration to an ETL they do this by altering the ETL in the ETL tool and saving the ETL to the custom\core\etl folder. All modified ETL's are saved to the custom\core\etl folder instead of the core\etl folder. The build script will give precedence to the contents of the custom folder. When exporting from the ETL tool to the custom\core\etl folder the customer will separate each ETL into a separate file instead of exporting to one, single file. The purpose of this is to allow concurrent development and to make it easier to import/export individual ETL's to the ETL tool.