1. A method for supporting data flexibility in a business intelligence (BI) server associated with a data warehouse, comprising: receiving a data flow information for the data warehouse from a extender associated with the data warehouse, wherein the data flow information indicates the mapping relationship between one or more source data objects and one or more target tables in the data warehouse; allowing a user to select the one or more target tables to be extended based on the data flow information; and building an input extension specification for the extender to extend the data warehouse.