Tools providing a flexible selection framework for automated processes. The framework can allow end-users to define their own selection criteria to select a data population to be processed (for example, by a business application). Hence, the tools provide enhanced control over what data is provided to which process. Some such tools employ metadata to define what information the client process needs, how the results will be returned to the client process, and/or what selection tools should be available to select data for the client process, as well as the available data selection tools, which can include both tools provided with a business application as well as third-party and/or user supplied selection tools. The framework might also provide an application programming interface that ensures consistent communication between the population selection engine and the selection tools themselves.