18.104.22.168 The Archival Information Package
An Archival Information Package (AIP), which is modeled in figure 4-15, is a specialization of the Information Package. The AIP is defined to provide a concise way of referring to a set of information that has, in principle, all the qualities needed for permanent, or indefinite, Long Term Preservation of a designated Information Object. The AIP is itself an Information Object that is a container of other Information Objects. Within the AIP is the designated Information Object, and it is called the Content Information. Figure 4-15: Archival Information Package (AIP)
Also within the AIP is an Information Object called the Preservation Description Information (PDI). The PDI contains additional information about the Content Information and is needed to make the Content Information meaningful for the indefinite Long Term.
The Preservation Description Information requirements in an AIP are much more stringent than the requirements for Preservation Description Information in the general Information Package. While no PDI objects are mandatory in an Information Package, all classes of PDI information must be present in an AIP. This is illustrated in figure 4-16. The contents of each type of PDI are left to the discretion of the individual Archive.
For example, in some OAIS holdings a statement that the creator of the Content Information is unknown may be adequate Provenance Information while in other OAIS holdings it may be mandatory that more complete provenance be researched.
Figure 4-16: Preservation Description Information
The AIP is delimited and identified by the Packaging Information. The Packaging Information may actually be present as a structure on the media that contains the AIP or, it may be virtual in that it is contained in the OAIS Archival Storage function. However, the delimitation and internal identification functions must be well defined in an OAIS.
Each AIP is associated with a structured form of Descriptive Information called the Package Description, which enables the Consumer to locate information of potential interest, analyze that information, and order desired information. The information needed for one Access Aid is called an Associated Description. A single Package Description may contain several Associated Descriptions depending on the number of different Access Aids that can locate, visualize, retrieve or order the associated Content Information and PDI. Figure 4-17 is a UML diagram that models the Package Description and Access Aids.
Figure 4-17: Package Description
The Package Description must contain one Associated Description that supplies data for a Retrieval Aid that allows authorized users to retrieve the Content Information and PDI described by the Package Description. This Retrieval Aid is generally part of the Archival Storage functional area. It translates from the unique identifier assigned by the OAIS to identify the AIP into the set of operations and filenames needed to retrieve the AIP from the file management system used in Archival Storage, and then returns the Content Information and PDI for the requested AIP. In most current Archives, only internal Archive processes and operations personnel and functions are authorized to use this Access Aid. However, as technology advances increase the processing power of the Archive and the bandwidth between the Archive and the user, such access methods as ‘content based queries’ and ‘data mining’ may provide the user with direct read-only access to the Content Information.
The Package Description may also contain any number of Associated Descriptions, each of which contains data for one or more Access Aids. Two additional subtypes of Access Aid are Finding Aid and Ordering Aid.
A Finding Aid is an application that assists the Consumer in locating information of interest. A single AIP may have a number of Associated Descriptions that describe the Content Information using different technologies.
An Ordering Aid is an application that assists the Consumer to discover the cost of and order AIPs of interest. The Ordering Aids also allow users to specify transformations to be applied to the AIPs prior to dissemination. These transformations can include Data Object transformations such as subsetting, subsampling or format transformations. The transformations can also involve modifying the PDI in the AIP prior to dissemination.
The Package Description is not required for the Long Term Preservation of the Content Information but is needed to provide visibility and access into the contents of an Archive. The contents of the Package Description are highly dependent on the structure of the Content Information and PDI it describes. The uses and types of Package Descriptions in an OAIS are further defined in 22.214.171.124.
Figure 4-18 gives a detailed view of the Archival Information Package by expanding the PDI and the Content Information. All the ‘contains’ relationships discussed in this subsection are logical containment relationships. This type of containment relationship may be physical or may be accomplished via a pointer to another object in storage, so an AIP is not necessarily a single file.
Figure 4-18: Archival Information Package (Detailed View)