66th IFLA Council and General
Jerusalem, Israel, 13-18 August
Code Number: 033-82(WS)-E
Division Number: VI
Professional Group: Information Technology
Joint Meeting with: National Libraries: Workshop
Meeting Number: 82
CDNL/CENL activities with identifiers
Titia van der Werf
The Hague, The Netherlands
As they extend their deposit tasks to include the safekeeping of born-digital publications, National Libraries have a special interest in persistent identifiers for digital material. Persistent identifiers and their resolution to deposit locators in a networked environment are key to the long-term accessibility of deposit collections
CDNL (the Conference of Directors of National Libraries) formed a Task Force to investigate these issues and, a year later, endorsed the Principles and Recommendations issued by the Task Force. On recommendation by the Task Force, CDNL has assumed responsibility for the administration of the National Bibliography Number (NBN) namespace for national libraries. First steps are taken to establish a global identifier infrastructure for deposit collections in a networked environment. Within this global framework, national bibliography numbers are unique and can be resolved to access the associated bibliographic descriptions and the corresponding deposit items. NBNs than, can be used globally to access deposit collections around the world. CDNL still needs to address major organisational and technical implementation issues. The Task Force will continue working on these issues on a step by step basis.
CDNL Task Force on Persistent Identifiers
National Libraries are responsible for the long-term preservation and availability of publications and other documentary heritage. As they extend their deposit tasks to include the safekeeping of born-digital publications, National Libraries have a special interest in persistent identifiers for digital material. Persistent identifiers and their resolution to deposit locators in a networked environment are key to the long-term accessibility of deposit collections.
The issue was raised at CDNL (the Conference of Directors of National Libraries), which formed a Task Force consisting of representatives from the national libraries of Australia, Canada, Finland, Germany, Netherlands and the United States, with Winston Tabb from the Library of Congress as chair.
The Task Force met twice: once in Washington DC on April 28-30, 1999 and once in The Hague on March 23-24, 2000. In this session I will present the main results achieved by the Task Force to date and future directions.
National Libraries and their use of identifiers
National Libraries use identifiers in a variety of ways:
In the networked digital environment the use of identifiers is changing because of the resolution functionality whereby the identifier serves as a locator. In this environment National Libraries are experimenting with new types of identifier usage:
- to facilitate bibliographic control by acting as agents responsible for assigning ISBNs, ISSNs, ISMNs, etc.,
- to facilitate the distribution and control of the bibliographic and authority records they create by assigning identifiers to the records themselves such as the national bibliographic number (NBN),
- to facilitate the acquisition process of publications by using the publisher's or other identifiers for order handling,
- to support the local management of the deposit collections by using locally assigned shelf numbers or URLs.
- to facilitate direct end-user access to digitised collections by using an identifier assigned by the library as the producer of the digital image,
- to facilitate permanent access to networked resources made available by other content producers, for example by establishing PURL services or URN generators,
- to facilitate linking from the catalogue record describing a networked resource directly to the resource itself, for example by using URLs as hyperlinks in the catalogue,
- to facilitate citation to a networked resource that is also available in a deposit collection, by publishing last-resort URLs
New challenges posed by identifiers in a networked environment
Issues arising from these new application areas are related to more general problem areas encountered in other sectors as well, such as:
- granularity: the level of specificity required of the identifier to identify a digital object as a whole and/or its component parts and the relationship with the granularity of the corresponding description;
- metadata: a fundamental relationship exists between identifiers and metadata. Which metadata is required to complement the function of identification? Distinctions between identifiers and metadata tend to become blurred as identifiers contain meaningful metadata (e.g. version information) and hyperlinks to catalogue entries are used to identify and locate digital objects.
- persistence of identifiers and persistence of resolution: this is mainly a responsibility issue. If national libraries are assuming responsibility for assigning and controlling persistent identifiers to digital objects made available by others, in how far should they also assume the responsibility for managing the associated resolution service? where does this responsibility end and where does the responsibility of the content provider for local URL management start?
- plurality of identifier systems: it is recognised that libraries will have to deal with digital objects that have been assigned different identifiers by different authorities. The various identifiers for a digital object will likely be dependent on different resolution services. In order to ensure effective linking from the bibliographic description to the digital object, libraries will be dependent on the chain of interdependent technologies supporting the links, including the different resolution services and the integrity of the links between the identifiers and the current physical addresses of the object.
CDNL Guiding Principles on Identifier Systems
The CDNL Task Force on persistent identifiers has issued Guiding principles for the development of identifier systems. The principles were endorsed by the CDNL meeting during the previous IFLA conference in Bangkok. The CDNL "Principles" underline the need for an identifier infrastructure, such as emerging in the web publishing community, not only to support electronic commerce but also to facilitate access and retrieval of networked resources. The "Principles" stress that the international library community has a partnership role with content providers in establishing how the relationship between identifiers and metadata will evolve. They recognise the need for interoperable identifier systems within an architectural framework that "should be based on open, international standards and accessible to the broadest range of information providers without prejudice and within reasonable costs". In addition, "the identifier scheme should be in the public domain", and "the charges for assignment and administration of identifiers, if any, should be on a not-for-profit basis". Finally, the global resolution services should be universally accessible, as distinct from access to the resources identified which, it is recognised, may fall under a given access control regime. Last, but not least, the "Principles" recognise the responsibility of memory organisations, such as national libraries, "to provide last-resort resolution services for identifiers of cultural heritage resources".
CDNL will promote adherence to these principles at large. It has given its technical working group the mandate to:
- promote the development of standards for persistent identifiers and the supporting infrastructure for resolution services
- liaise with other parties engaged in these developments, particularly content producers and publishers, web-technology developers, such as the World Wide web Consortium (W3C) and the Internet Engineering Task Force (IETF), and implementers such as the web-browser community.
CDNL establishes a shared URN namespace
On recommendation by the Task Force, CDNL has assumed responsibility for the administration of the National Bibliography Number (NBN) namespace for national libraries and designated the Library of Congress as its agent to act on its behalf as the registry for that shared namespace. Helsinki University Library, the National Library of Finland, is in the process to register the NBN as a URN namespace identifier with the IETF.
These first steps are taken to establish a global identifier infrastructure for deposit collections in a networked environment. Within this global framework, national bibliography numbers are unique and can be resolved to the associated bibliographic descriptions and the corresponding deposit items. NBNs than, can be used globally to access deposit collections around the world.
The concept of "National Bibliography Number" is generic and refers to a group of identifier systems used by national libraries for identification of deposit collection item descriptions and in some case also for identification of the corresponding deposit items. To date, each national library has used its own NBN string independently of other libraries, there has been no global authority to control the assignment of NBNs. For this reason NBNs are unique only on the national level.
To make the use of NBNs unique on a global scale it is proposed to add a prefix, which may be a country code or another code, registered with the NBN Prefix Registry at the Library of Congress.
Examples of NBNs used as URNs:
URN:NBN:fi-fe19981001 (a "real" URN assigned by the National Library of Finland.)
URN:NBN:LCCN2001000168 (a LCCN-based hypothetical URN assigned by the Library of Congress)
In addition to this, a global resolution system will have to be put in place to actually enable the use of NBNs as URNs. A NBN Resolution Service needs to be established, probably based on the existing Domain Name System (DNS) architecture, to re-direct a NBN to the resolution service identified by the NBN-prefix. From there on the NBN will be resolved at the national or local level of the organisation(s) involved. The final step in the resolution will take place at the level of the national bibliography database. This database contains the resource description and the URL to the actual resource in the deposit system.
This resolution system will rely heavily on the quality of service of each participating deposit library system. Best practice guidelines and promotional activities will be necessary to ensure large-scale deployment of this proposed NBN-as-URN mechanism.
CDNL still needs to address major organisational and technical implementation issues. The Task Force will continue working on these issues on a step by step basis.
CDNL will promote the Guiding Principles and raise awareness within the library community of the need for an identifier infrastructure to facilitate access and retrieval of networked resources. It will promote liaison with other parties that can help progress the establishment of this identifier infrastructure. It has tasked its Task Force on Persistent Identifiers to proceed with the establishment of the NBN Namespace. The National Library of Finland will register the namespace and the Library of Congress will issue guidelines for the NBN SubPrefix Registry. The Task Force will look into issues concerning the maintenance of the integrity of the NBN and the management of URLs in library deposit systems.
All these steps, and more to come in the future, will help advance the establishment of a global identifier infrastructure for better access to deposit collections.