Unique permanent referencing and reliable citation of online resources

The Uniform Resource Name (URN) is a Persistent Identifier (PI) with which – unlike URLs – online resources can be uniquely and permanently identified regardless of where they are stored. URNs ensure that online resources will remain available in the long term. The German National Library administrates and assigns URNs from the namespace “urn:nbn:de” and offers a URN resolving service for Germany and Switzerland (Information on URN at the Swiss National Library).

URN structure

URN:nbn:de:[SNID]-[NSS]

Element	Description
URN:	URI-Schema
nbn:	National Bibliography Number
de:	Country Code
[SNID]	Subnamespace Identifier
[NSS]	Namespace Specific String

If the publication is moved to a different storage location, e.g. if there is a change in servers, the access address (URL) linked with the URN can be corrected. In this way, the URN keeps its validity and continues to refer to the corresponding publication. URLs are updated centrally by the URN service, ensuring that the relevant URN remains stable and the link to the relevant publication is maintained.

Our URN service has important advantages for academics, authors, publishers, information brokers and archives:

• Reliable referencing of digital objects
• The use of URNs guarantees the provision of durable, consistent, stable links in library catalogues and portals
• Less work involved in maintaining permanent access to the document

You can use the URN service free of charge.

URN resolver

The urn:nbn-resolver for Germany and Switzerland is a central component of the URN service. When you enter a URN, you are directed to the referenced object via the URLs stored in the database.

You can reach the resolver at https://nbn-resolving.org/?siteLang=us

Adding the resolver link to the URN (example: urn:nbn:de:example) makes the URN operable (example: https://nbn-resolving.org/urn:nbn:de:example); it can then be directly inserted in websites, catalogues or documents as a link.

If the website sends a temporary or permanent error message to the resolver, the user will not be taken straight to the website. Instead, all the URLs stored in the URN database will be listed on an information page.

Example for URN
urn:nbn:de:bvb:91-diss20060308-1417541491

with the associated URLs

• http://mediatum.ub.tum.de/node?id=602680
• http://mediatum.ub.tum.de/doc/602680/document.pdf
• http://d-nb.info/979049504/34

Get detailed technical information in the URN resolver API documentation (only available in German).

URN for online publications in our collection

All online publications archived by the German National Library are assigned an URN from the namespace "urn:nbn:de".

The amendment to the Law Regarding the German National Library in 2006 extended our collection mandate to encompass online publications. This means we are responsible for the long-term archiving of digital publications, a task which includes persistent identification through the assignment of URNs. (Long-term Preservation Policy ). The German National Library normally assigns these automatically from the subnamespace urn:nbn:de:101:1. Exceptions apply to larger organisations.

The German National Library adopts other Persistent Identifiers such as DOI, Handle or ARK when collecting online publications and records them in the metadata.

URNs in a separate subname­space for URN partners

In certain circumstances, we offer institutions and publishers the option to manage their own subnamespace in the namespace urn:nbn:de and to register URNs in it. This facilitates the free assignment of URNs in a defined space but also obliges the user to assume responsibility for the URNs being correct and resolvable in the long term.

You will find the conditions associated with separate subnamespaces and the principles used to assign URNs in the Policy for issuing URNs in the urn:nbn:de namespace (version 1.0 last updated 29 November 2012). URN subnamespaces are registered by the German National Library. If you are interested, please send an e-mail to urn-support@dnb.de.

At present, around 400 URN partners manage URNs in their own subnamespaces.

Total number of URNs in the namespace urn:nbn:de

More than 48 million URNs were registered in the namespace urn:nbn:de by the end of 2021.

Source: German National Library

Transfer interfaces for URN registration and maintenance

URN partners who manage URNs from their own subnamespace have three options for registering and updating their URNs.

• REST-API
• Web form
• OAI interface in xepicur format

REST-API

As a new option, we are now offering our URN partners the use of a REST-API, which is currently undergoing productive testing with the first partners. This has the following advantages compared to other processes:

• Our URN partners have control of the transfer of data: when using the REST interface, you yourself can decide when, how often and how much of your data is transmitted to us.
• Direct feedback from the system allows for more transparency and greater process control.
• Improved traceability and process overview for our URN partners.
• Technically a low-threshold solution.

You will find more information about the interface in the URN service documentation at URN service API (only available in German). Please get in touch with us if you are interested.

The new REST-API is another machine interface for the registration and upkeep of your URNs.

Web form

This transfer method facilitates the manual entry of URNs if it is expected that only a small number of URNs will be administrated.

You can use this web form:

https://admin.nbn-resolving.org/

You can use the web form to

• generate URNs
• register individual URNs
• delete or add URLs to registered URNs

URN administration using the protocol OAI-PMH 2.0

You can use the OAI interface to

• register one or more URNs
• delete or add URLs to registered URNs

Procedure

1. Setting up an OAI interface with the help of the metadata format “epicur” (written in exactly this way)
2. Delivery of valid metadata in xepicur format

The metadata provided must be structured according to xepicur rules.

More information about xepicur

xepicur – XML data transfer format for the administration of Persistent Identifiers (Reference description)

XML-Schema <urn:nbn:de:1111-2004033116>