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; employing the artifact to retrieve the data object by searching among the set of data processing systems to locate a data processing system in the set that stores the data object, wherein the searching comprises: receiving a retrieval request from the first data processing system at a second data processing system, wherein the retrieval request contains the artifact; searching a local datastore of the second data processing system using the artifact; in response to a determination that the data object is stored within a local datastore of the second data processing system, sending a retrieval response from the second data processing system to the first data processing system, wherein the retrieval response contains the data object; and deleting the data object from a local datastore of the second data processing system; and returning a data object retrieval response from the first data processing system to the first federated entity.