Workbook on Digital Private Papers > Administrative and preservation metadata > Persistent identifiers
Persistent identifiers
Persistent identifier schemes
Introduction
Persistent identifiers have existed for a long time in the library world in the form of schemes like the International Standard Book Number (ISBN) and Library of Congress Control Number (LCCN). Their importance is also recognised in the archive world: ISAD(G)2 sets out the requirements for a globally unique and persistent archival reference code. At collection level, this consists of: a country code, in accordance with ISO 3166; a repository code in accordance with the national repository code standard (in the UK, this is the ARCHON reference); and a specific local reference code.
Example from the John Rylands University Library: GB-133-RMD.
This is the collection-level code for the Papers of Ramsay MacDonald. The local code is based on a 3-letter mnemonic, and a register of mnemonics is maintained centrally so the same code is not used twice.
Since moving into the digital age the issue of PIDs has become increasingly important, and recent debates over PIDs largely focus on the issue of actionable or resolvable identifiers, i.e. unique names which not only persist over time but will also take the user to the identified archival digital object or to information about that object.
A number of PID schemes are in use in the digital environment; these have been developed by different communities, and some are more suited to certain contexts than others. An institution or sector may find that some elements from a number of different schemes are suitable for their use rather than any one scheme in its entirety; conversely, in some cases none of the existing schemes may be appropriate, in which case an institution may consider implementing an independent solution.
If taking the latter approach, the importance of future interoperability should be taken into account; a local scheme should be capable of integration into any wider schemes in operation (either within the same community or globally), which means that adhering to open standards is important. Most of the PID schemes currently in place are still under development, and it may be that some of them do not survive in the long term; however, this situation does give organisations the opportunity to feed into the development of identifier schemes and to work with similar institutions to develop shared solutions.
Probably the most important component of any PID scheme in ensuring persistence is commitment from the organisation, and ensuring that the scheme is administered comprehensively - ultimately a PID can only be associated permanently with any one resource if there is a commitment to maintaining that link; it cannot happen automatically.
An introduction to some of the principal PID schemes follows. This includes: their historical background, how they work, their syntax, the extent of their adoption and who maintains them. The advantages and disadvantages of each scheme are considered from the perspective of an institution which collects the digital and hybrid personal archives of significant individuals such as politicians. No single scheme is picked out as the best, because each institution is likely to have slightly different practices and requirements. Given that such a large proportion of personal archives are likely to be closed for long periods because of data protection and copyright restrictions (see Chapter 09 Legal issues), the best approach may be to implement a basic local identifier system which complies with the URI and URN standards and await the widespread adoption of a universal URN resolver.
