Editing ISSN (section)

== Use in URNs ==
An ISSN can be encoded as a [[uniform resource name]] (URN) by prefixing it with "{{code|urn:ISSN:}}".{{Ref RFC|3044}} For example, [[Rail (magazine)|''Rail'']] could be referred to as "{{code|urn:ISSN:0953-4563}}". URN namespaces are case-sensitive, and the ISSN namespace is all caps.<ref>{{cite web|url=http://dublincore.org/architecturewiki/ResourceIdentifierGuidelines#head-a2100b457f3211cf98e960a3a481007893c4e68a |archive-url=https://web.archive.org/web/20120513221344/http://dublincore.org/architecturewiki/ResourceIdentifierGuidelines |archive-date=13 May 2012 |title=Guidelines for using resource identifiers in Dublin Core metadata §4.5&nbsp;ISSN |last1=Powell |first1=Andy |last2=Johnston |first2=Pete |last3=Campbell |first3=Lorna |last4=Barker |first4=Phil |date=21 June 2006 |website=Dublin Core Architecture Wiki |url-status=dead }}</ref> If the checksum digit is "X" then it is always encoded in uppercase in a URN.

=== Problems ===
The URNs are [[#Media versus content|content-oriented]], but ISSN is media-oriented:

* '''ISSN is not unique''' when the concept is "a journal is a set of contents, generally copyrighted content": the same journal (same contents and same copyrights) may have two or more ISSN codes. A URN needs to point to "unique content" (a "unique journal" as a "set of contents" reference).
:Example: [[Nature (journal)|Nature]] has an ISSN for print, 0028-0836, and another for the same content on the Web, 1476-4687; only the oldest (0028-0836) is used as a [[unique identifier]]. As the ISSN is not unique, the [[U.S. National Library of Medicine]] needed to create, prior to 2007, the NLM Unique ID (JID).<ref>{{cite web |url=https://www.nlm.nih.gov/bsd/mms/medlineelements.html#jid |title=MEDLINE/PubMed Data Element (Field) Descriptions |date=7 May 2014 |publisher=U.S. National Library of Medicine |access-date=19 July 2014 |archive-date=27 April 2019 |archive-url=https://web.archive.org/web/20190427130927/https://www.nlm.nih.gov/bsd/mms/medlineelements.html#jid |url-status=live }}</ref>
* '''ISSN''' does not offer [[uniform resource name#Resolvers|resolution mechanisms]] like a [[digital object identifier]] (DOI) or a URN does, so the DOI is used as a URN for articles, with (for historical reasons) no need for an ISSN's existence.
:Example: the DOI name "10.1038/nature13777" can be represented as an HTTP string by <code>''<nowiki>https://doi.org/</nowiki>''10.1038/nature13777</code>, and is [[URL redirection|redirected]] (resolved) to the current article's page; but there is no ISSN online service, like <code><nowiki>http://dx.issn.org/</nowiki></code>, to resolve the ISSN of the journal (in this sample [[Nature (journal)|1476-4687]]).

A unique URN for serials simplifies the search, recovery and delivery of data for various services including, in particular, [[information retrieval|search systems]] and [[knowledge base|knowledge databases]].<ref name="issnL" /> '''ISSN-L''' (see [[#Linking ISSN|Linking ISSN]] above) was created to fill this gap.