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 identify a data processing system within the set of data processing systems as having generated the artifact, the employing step determining that the extracted tag identifies a second data processing system as having generated the artifact; sending a retrieval request from the first data processing system to the second data processing system, wherein the retrieval request contains the artifact; receiving the retrieval request from the first data processing system at the second data processing system; searching a local datastore of the second data processing system using the artifact; retrieving the data object that is referenced by the artifact; sending a retrieval response from the second data processing system to the first data processing system, wherein the retrieval response contains the data object; receiving a retrieval response from the second data processing system at the first data processing system; and returning a data object retrieval response including the data object from the first data processing system to the first federated entity.