Responsive to a request to access heterogeneous repositories, a REST server queries a resource registry to find resources that match mapping information contained in the request. The resource registry returns resource registry tables containing the matching resources. The resource registry tables implement a unified data structure of a resource registry model and are generated at runtime by the resource registry mapping REST service configuration parameters to the fields of the unified data structure. The REST service configuration parameters are added to an extension SDK for REST extension developers to enhance REST service configuration for extension applications. The REST service configuration parameters are configured at implementation time and loaded/scanned into the REST server at runtime. The REST server iteratively evaluates the resource registry tables until all the matching resources have been evaluated. The evaluation result is used to determine whether to reject, accept, or redirect the request from the client device.