The repository shall have access to necessary tools and resources to provide authoritative Representation Information for all of the digital objects it contains.

This is necessary in order to ensure that the repository’s digital objects are understandable to the Designated Community.

Subscription or access to registries of Representation Information (including format registries); viewable records in local registries (with persistent links to digital objects); database records that include Representation Information and a persistent link to relevant digital objects.

These tools and resources can be held internally or can be shared via, for example, a trusted set of registries. However, this requirement does not demand that each repository has such tools and resources, merely that it has access to them. For example a repository may access external registries.1 Any such registry is a specialized type of repository, which itself must be certified/trustworthy. The repository may use these types of standardized, authoritative information sources to identify and/or verify the Representation Information components of Content Information and PDI. This will reduce the long-term maintenance costs to the repository and improve quality control. Sometimes there is both general Representation Information (e.g., format information) and specific Representation Information (e.g., meanings of individual fields within a dataset). Often the general information will be available in an external repository, but the local repository may need to maintain the instance-specific information. It is likely that many repositories would wish to keep local copies of relevant Representation Information; however, this may not be practical in all cases. Even where a repository strives to keep all such information locally there may be, for example, a schedule of updates which means that until an update is performed, the local Representation Information is incomplete. This may be regarded as a kind of local caching of, for example, the Representation Information held in registries. Alternatively one may say that in these cases, the use of international registries is not meant to replace local registries but instead serve as a resource to verify or obtain independent, authoritative information about any and all Representation Information. Good practice suggests that any locally held Representation Information should also be made available to other repositories via a trusted registry. In addition any item of Representation Information should itself have adequate Representation Information to ensure that the Designated Community can understand and use the data object being preserved.

APTrust has both a WebUI (in the form of Registry) and a REST API. Both provide Representation Information about AIPs in the form of Intellectual Objects and Generic Files and contain persistent links to their preservation space. Documentation about these interfaces can be found on the page Member API.