4.2.1.1 Identify which definition applies to which AIP

4.2.1.1 - The repository shall be able to identify which definition applies to which AIP.

The CLOCKSS archive has a single class of AIP, called an Archival Unit (AU), documented in Definition of AIP. Part of that documentation describes the Reference information that forms part of the Preservation Description Information (PDI) of an AIP (AU):

• Context: the context information for an AU consists of:
  • The plugin ID, which is the encoded name of a Java class implementing the LOCKSS plugin interface.
  • The parameters, which are a set of {name, value} pairs providing the arguments needed to construct an instance of the class named by the plugin ID.

  In effect, the context for the AU is a customized instance of a Java class, normally referred to as its plugin. It is thus executable, capable of performing operations on the AU such as adding content and metadata from a SIP (see below), extracting metadata, and taking part in integrity checks.

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• Reference: Each AU has an immutable internal name, computed from its context information and stored with it. The software locates it in the POSIX filesystems using a map from this internal name to the path to the AU's root directory which is built during system startup and subsequently maintained as new AUs are created. Content within an AU can be located by querying the metadata database using specific bibliographic metadata fields to match against the bibliographic metadata supplied by the publisher or derived from the AU's context.

Thus the AU's PDI ensures that the appropriate instance of the appropriate Java class is used when parsing or interpreting the AU (AIP).

Relevant Documents

1. Definition of AIP
2. LOCKSS: Extracting Bibliographic Metadata
3. LOCKSS: Metadata Database