1. A method for supporting data flexibility in a business intelligence (BI) server associated with a data warehouse, comprising: providing an extender associated with a data warehouse, wherein the extender is implemented in Java and wrapped by a remote service, and communicates with an administration tool on the BI server through a Java host; providing, from the extender, data flow information to the administration tool, wherein the data flow information includes dependencies between target tables in the data warehouse, and specifies mapping relationships between a plurality of source data objects and the target tables in the data warehouse; receiving, from the administration tool, an input extension specification that includes one or more changes in the source data object, and one or more target tables to be extended using the one or more changes, wherein the input extension specification is constructed by the administration tool based on the one or more changes and the data flow information, wherein the extender receives the input extension specification as values of a plurality of input parameters of a function call from a Java client, which forwards the function call from the Java host in response to the administration tool making a call to the remote service through the Java host; retrieving, via the extender, a metadata for a repository model of the data warehouse, and an extract, transform and load (ETL) metadata for the data warehouse, from a metadata server associated with the BI server; extending the ETL metadata using the input extension specification and the metadata for the repository model of the data warehouse; invoking, via the extender, an implementation module specific to the data warehouse to extend the one or more target tables in accordance with the extended ETL metadata; generating, by the extender, an output document that contains information on tables created, modified, or searched in the data warehouse by the implementation module, and information on columns, keys and references associated with the tables created, modified or searched; and providing the output document to the administration tool, wherein the output document is configured to be used by the administration tool to modify the repository model of the data warehouse stored in the metadata service.