It is most sensible for the DHF to be a living document, as updates are made and the design revised, it must be permanently logged. Even post design transfer, it is important to update the origin of these designs so that it is in a central location, instead of some being scattered in the DMR. While this school of thought is the most logical, it is not always followed this way, especially for very old devices that have been updated over a series of decades. For example, in our company there are many revisions to the SOP of device manufacturing, from small changes in the location of a gage to a whole process being reconfigured. This change is not added to the DHF but instead is appended to the DMR as there have been a vast number of revisions over an extended period of time. Ideally, if this was the practice from the beginning of the device life, keeping the DHF as a living document would be more feasible.