The repository shall assign and maintain persistent identifiers of the AIP and its components so as to be unique within the context of the repository.

This is necessary in order that actions relating to AIPs can be traced over time, over system changes, and over storage changes.

Documentation describing naming convention and physical evidence of its application (e.g., logs).

A repository needs to ensure that there is in place an accepted, standard naming convention that identifies its materials uniquely and persistently for use both in and outside the repository. The ‘visibility’ requirement here means ‘visible’ to repository managers and auditors. It does not imply that these unique identifiers need to be visible to end users or that they serve as the primary means of access to digital objects. Ideally, the unique ID lives as long as the AIP; if it does not, there must be traceability. Subsection 4.2.1 requires that the components of an AIP be suitably bound and identified for long-term management, but places no restrictions on how AIPs are identified with files. Thus, in the general case, an AIP may be distributed over many files, or a single file may contain more than one AIP. Therefore identifiers and filenames may not necessarily correspond to each other. Documentation must represent these relationships.

The identifiers are persistent. The semantic identifiers don’t change, they stay the same. Those are the identifiers that include the depositor domain, the name of the baf and the path of the file within the original bag.

These are not DOIs registered anywhere else besides the system and depositors have it in their own internal systems.

APTrust bags consist of a bag directory named using a combination of the owning institutional identifier and the persistent identifier of the object being preserved as supplied by the originating institution.  The bag MUST contain at least one manifest file with fixity information for files in the data subdirectory, a bagit.txt file as required by the specification, a data directory to contain preserved files and a bag-info.txt file using several fields to help managed ownership of the bag as well as an aptrust-info.txt tag file for APTrust specific metadata not covered by the bag-info.txt file.

Full description of this process is described at Bagging specifications#How Bag Names Become Object Names