oais1.jpgNoted from OAIS.

The OAIS reference model groups all the various processes happening within an archive into six basic entities.

The Ingest entity receives the SIP and turns it into an AIP  for storage within the OAIS. This is the point at which a record may migrate from one file format to another. The Ingest people do detailed technical negotiating with Producers, create the Descriptive Information, check the record’s authenticity and so on.

The Archival Storage entity is responsible for the physical storage and maintenance of the bitstream. The AS people carry out periodic media refreshing, and reconstruct the AIPs after a  system failure.

The Data Management entity is responsible for the intellectual aspects of AIP storage. The DM people administer the overall database which runs the system and which stores the catalogue Descriptive Information. They also have the wider function of agreeing and applying the OAIS’s policies and procedures, and according to section 1.7.2 they carry out Consumer billing and keep statistics of Consumer access (which I imagine could also be carried out by the Access entity people).

The Access entity makes holdings visible to Consumers. It allows the user to search the archive’s contents, creates DIPs, and monitors their delivery.

Underlying all these is the Administration entity which essentially monitors the OAIS’s operation, analyses ways of optimising the system, negotiates with Producers and so on.

Finally the OAIS needs to monitor the changing technological context in which it operates. This is the responsibility of the Preservation Planning entity. The PP people monitor wider developments in HW and SW, check whether stored AIPs can be rendered on forthcoming systems, and decides on the best strategy for changing circumstances (eg whether to emulate or to migrate).

No explanation of the OAIS model is complete without a diagram, so here’s one re-drawn from figure 4-1 in the Model, showing how the entities relate.