4.1.2 DATA FLOW DIAGRAMS
The flow of data items among the OAIS functional entities is diagrammed in this subsection. Figure 4-8 shows the more significant data flows. To avoid complicating this figure, the Administration data flows, which are generally background activities, are isolated to an Administration context diagram, figure 4-9. Data flows associated with Common Services are implicit in the illustrated functions, and are therefore not shown.
Figure 4-8: OAIS Data Flow Diagram
Figure 4-9: Administration Context Diagram
A significant data flow that is not obvious is that which involves the update of AIPs in order to ensure they are adequate for preservation of the Content Information.
For example consider the case of needing to add Representation Information because of changes in the Knowledge Base of the Designated Community. Although the Data Object that is being preserved is not being changed, the need to change the Representation Information means the Content Information is being changed. This is in general terms a Migration of the AIP.
– Monitoring of the Designated Community and general environment (reports, requirements alerts, emerging standards, external data standards, prototype results and technology alerts) shows the need to update Representation Information for a particular AIP, which could itself be a collection of objects.
– Preservation Planning provides recommendations, proposals and risk analysis reports to Administration which evaluates the recommendations and decides what options to look at in more detail, and sends that decision to Preservation Planning as approved standards, preservation requirements and migration goals. – Preservation Planning then produces detailed plans based on the instructions from Administration and passes these detailed plans back (AIP templates, migration packages and customization advice) to Administration.
– Administration then implements these plans (via Manage System Configuration). In general this will require an update (logically or physically) of one or more AIPs. The next steps may be done logically; i.e., the AIP does not necessarily have to be moved in any way.
– Instructions are then sent to Access (dissemination request) to send the original AIP out as a DIP which is then received by Ingest, together with the updated Representation Information.
– On Ingest a new AIP version is created (in Generate AIP) containing the updated Representation Information.
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