Persistent Identifiers for multiple resources in all sectors of culture
How can cultural resources – physical or digital books, files, films, artworks and such like – be allocated a distinct and permanent address so that the associated digital information can be located efficiently on the internet? At the “Mitten im Wandel” Colloquium for archiving processes and technology (24th-27th November 2014) a group of authors representing the German National Library, the Deutsche Digitale Bibliothek, the Federal Archives and the Landesarchiv Baden-Württemberg presented their concept for a service that enables the issuing of cross-sectoral persistent identifiers (PIs).
What are Persistent Identifiers?
A persistent identifier (PI) is a reference code consisting of a one-off, albeit standardised, sequence of characters that enables a specific resource to be clearly and permanently identified.
However, a PI is not simply an unambiguous label for a particular resource; it also forms the basis for accessing, in conjunction with a ‘resolution service’, the labelled resource and information associated with it. A resolution service stores the link between an immutable PI and a modifiable URL. When the resolution service transforms a persistent identifier, this has the effect of assigning a URL to the PI, which in turn leads directly to the resource.
Why are Persistent Identifiers necessary?
The stable and unambiguous labelling of both digital and physical cultural material is a key element in the digitisation process. If work with cultural material is to run smoothly, it is important that stable and unambiguous local identifiers are already being used within the cultural and scientific institutions. These identifiers are what enable us to give unambiguous labels to physical items (e.g. documents, museum objects) or digital resources (e.g. PDF or image files) and to locate and work with them. The identifiers can take a variety of forms (e.g. consecutive numbering, shelf marks, document reference numbers) and they guarantee the stability and retrievability of a particular local stock of material. It is also possible to monitor which resources have been collated, modified or even disposed of and to update resources at local level.
However, if these local identifiers are also to function at a global level – i.e. outside the particular institution – there are additional challenges to overcome. The aim is to use persistent identifiers to ensure cross-sectoral interchangeability and the interlinking and secure quoting of material and resources worldwide. This also leads to improvements in the quality of data.
Persistent Identifiers and the Deutsche Digitale Bibliothek
The work of the Deutsche Digitale Bibliothek has shown that the suppliers of data are not always able to provide stable and unambiguous identifiers. This has serious repercussions for the DDB and the cross-sectoral interlinking of material:
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- Objects in the DDB cannot be quoted consistently.
- The process of updating metadata results in the duplication of material.
- Information attached by users to an item (e.g. comments or favourite lists) is available only for a limited time.
- 4. Links to the content pages of data suppliers (‘Show object in data-supplier’s website’) are unstable. High risk of broken links.
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In view of its cross-sectoral nature the Deutsche Digitale Bibliothek has a vested interest in being able to issue, via a central service, uniform persistent identifiers for material stemming from archives, libraries, museums, research institutions and preservation organisations. We are therefore keen to provide our cooperating partners with the means to issue their own global, unambiguous persistent identifiers for their resources.
To this end we have come up with the cross-sectoral ‘CHE’ PI service – Persistent Identifiers for Cultural Heritage Entities. Initially designed jointly with representatives from the archiving sector, ongoing development of the model over the course of the year will involve representatives from other sectors.
The implementation of CHE is intended to draw on the experience of the German National Library, which already uses its own PI service (‘urn:nbn:de’) and by early 2015 had issued, and was actively administering, approx. 21,3 million PIs (albeit exclusively for digital resources and mainly in a library context). The German National Library also offers its services as operator of the CHE name environment and the resolution service.
Summary
Clearly identifiable physical resources – complete with digital representations -, which are integrated into a worldwide network, are key to the ‘Internet of Things’. This idea is being adopted by the CHE model and applied to the world of cultural and scientific institutions. Internationally stable and unambiguous identifiers form the foundation for the reliable and ongoing referencing and linking of material on the internet. Persistent identifiers are also important factors in the exchanging of resources between different parties, e.g. when platforms such as the Deutsche Digitale Bibliothek aggregate and present metadata and thumbnails from a variety of data suppliers. PIs facilitate the smooth exchange of data and make it possible to achieve correct preview images and stable links to the relevant resource on the data supplier’s site.
Links
che [at] listserv.dfn.de (Mailing list)
Contact
Deutsche Digitale Bibliothek
Michael Büchner, M. Sc., Technical Coordinator
Deutsche Nationalbibliothek
Adickesallee 1
60322 Frankfurt am Main
Tel +49 69 1525-1774
m.buechner [at] dnb.de (m[dot]buechner[at]dnb[dot]de)