1. A method for transferring data objects between federated entities in a federated computational environment, the computer-implemented method comprising: receiving a data object retrieval request from a first federated entity at a second federated entity, wherein the second federated entity issues artifacts for the first federated entity in accordance with a trust relationship between the second federated entity and the first federated entity, wherein services of the second federated entity are provided by a set of data processing systems within a distributed data processing system, and wherein each data processing system in the set of data processing systems generates artifacts; extracting an artifact from the data object retrieval request by a first data processing system in the set of data processing systems, wherein the artifact references a data object that is stored by the second federated entity; extracting a tag from the artifact, wherein each data processing system in the set of data processing systems is uniquely identifiable, wherein each artifact includes a tag, and wherein each tag has a value that indicates a data processing system within the set of data processing systems that generated a tag; and employing the extracted tag to identity a data processing system within the set of data processing systems as having generated the artifact.