1. A computer-implemented method for exchanging computer data in a data exchange between a first data processing system having a less restrictive data structure and a second data processing system having a more restrictive data structure, the method comprising: receiving, by a computing system, from the first data processing system that has deleted first data, an indication -that second data at the second data processing system corresponding to the first data is to be deleted; determining, by the computing system, whether a data structure associated with the second data processing system permits deleting the second data; only sending, by the computing system, to the second data processing system, the indication that the second data is to be deleted when the data structure associated with the second data processing system permits deleting the second data; and when the data structure associated with the second data processing system does not permit deleting the second data, instead sending by the computing system, to the first data processing system, data to be inserted to replace the first data which has been deleted.