Persisting a version history of MED stored in the registry will help determine if the MED the user wants to register is newer or older than the one in already in the registry. The MED business object does have a version number but there are problems with using that to determine if one MED is newer/older than another MED. For instance, in a multi-user environment the same MED could be updated by different users. Each user could end up with a MED with the same version but with different content. And those MEDs could end up in the hands of other users who could also create new versions. Of course an enterprise could be diligent about controlling MED versioning using their own version-control system and possibly get around this issue. With that said, persisting a MED version history by using something like a checksum/sha-1 would remove the problems associated with relying on the version number at least for a workspace. We might also look at writing an exporter/importer to export the version history and then import into another workspace.