The history component of an NDF provides a way of recording the processing operations which are performed on the dataset. It consists of a series of history records (with some ancillary information) each of which contains information about a particular processing operation and when it occurred. Normally, each of these operations will correspond with the execution of a single application which has either modified or created the NDF.
It is intended that the user of NDF applications should have considerable control over the recording of history information, but that writers of applications should not generally need to concern themselves with how this is achieved. Indeed, if a user has access to basic utilities for manipulating the history component of NDFs, then new applications will automatically provide history recording facilities without their authors making any specific provision for it. Most programmers may therefore need to read very little of this section except in special cases where explicit control over history recording is required.