For SMS, standard MIF files are called NOIDMIF files. These files do not contain a unique identifier for the data. They have no ID. SMS automatically associates NOIDMIF file data with the computer that the NOIDMIF files are collected from.
SMS also supports IDMIF MIF files. These files do contain a unique ID, and are not associated with the computer they are collected from. IDMIF files can be used to collect inventory data about devices that are in the vicinity of a computer, but not actually associated with it. For example, a shared network printer, video cassette recorder, photocopier, or similar equipment is not associated with any specific computer, but you might want to record data about it for asset management purposes. This data is stored in separate tables in the SMS site database.
IDMIF extensions (or custom DDRs) can also be used to create new tables in the SMS site database that you might need for reporting purposes. For example, you might have asset management data that is not strongly tied to individual computers. This data is not appropriate for NOIDMIF files or MOF extensions, but you want to join it with SMS data for reporting purposes.