Abstract: An extensible ETL framework can be designed with components/elements that add and manage request driven customizations to a database and that allow an ETL application to incorporate these customizations into its ETL process without code changes to the ETL application. The extensible ETL framework comprises a data aggregator element (“data aggregator”) that processes customization requests for a database. The data aggregator executes customization requests to create, update and delete custom attributes. The ETL application dynamically detects the custom attributes and associated metadata when executing. The ETL application uses the detected custom attributes and associated metadata to determine source data tables and data values to be extracted from the source data tables to incorporate the custom attributes into the ETL process being performed by the ETL application. The ETL application may alter target data tables that are then loaded with the extracted data values.