What is a URN identifier?
A URN identifier is a unique and persistent identifier of an electronic document. Once given to a document, the identifier remains unaltered as long as the name and the contents of the document remain intact. The same identifier is never assigned to two separate documents. The URN identifier can be exploited as a persistent web address through registering.
- The ISBN number of a document is 952-10-0093-7;
- the URN identifier of the document is therefore URN:ISBN:952-10-0093-7;
- the persistent web address of the document is thus http://urn.fi/URN:ISBN:952-10-0093-7.
The resolving server redirects to the current location of the document. When the document is moved, the change will be registered and thus the persistent address remains functional.
The publisher may register URN identifiers manually, but usually the data are updated automatically from the publisher’s system, for example, the institutional repository.
Generating a URN identifier
If a document is eligible for an ISBN or an ISSN number, it will be assigned one, and the URN identifier is based on it.
If a document cannot be given an ISBN or an ISSN number, it will be assigned an NBN number.
Identical copies of a document recieve the same URN identifier. Therefore, a URN based web address may resolve successfully to several URLs.
If a document is edited, a new URN identifier is only assigned if the contents change significantly.
- URN:NBN numbers are assigned to web documents only.
NBN numbers may be obtained from the URN generator maintained by the National Library. A publisher may apply for a NBN sub-namespace and generate numbers independently.
Displaying the URN identifier in a document
URN:ISBN and URN:ISSN identifiers must be both displayed in writing in the body of the document (if applicable) and recorded in its metadata.
In creating metadata, one can use the Dublin Core metadata generator.
The URN identifier is specified in the Internet standards of the IETF (Internet Engineering Task Force).
Using ISBN numbers as part of a URN identifier is specified in RFC 3187, ISSN numbers in RFC 3044, and NBN numbers in RFC 3188. URN syntax is specified in RFC 2141.
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