Internet Engineering Task Force (IETF)
Request for Comments: 8254
Obsoletes: 3044, 3187
Category: Standards Track
ISSN: 2070-1721
J. Klensin
J. Hakala
The National Library of Finland
October 2017

Uniform Resource Name (URN) Namespace Registration Transition


The original registration procedure for formal Uniform Resource Name (URN) namespaces required IETF Consensus. That requirement discouraged some registrations and increased the risk for problems that could occur as a result. The requirements have now been changed by RFC 8141, which adopts a different model, focusing on encouraging registration and publication of information for all appropriate namespaces. This document clarifies the status of relevant older RFCs and confirms and documents advice to IANA about selected existing registrations. This document also obsoletes RFCs 3044 and 3187 and moves them to Historic status. These RFCs describe the ISSN and ISBN namespaces, which are now outdated because the descriptions reside in registration templates.

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841.

Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at

Copyright Notice

Copyright © 2017 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents ( in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Obsoleting Older Registration RFCs for ISSNs and ISBNs  . . .   4
     2.1.  ISBN URN Changes  . . . . . . . . . . . . . . . . . . . .   4
     2.2.  ISSN URN Changes  . . . . . . . . . . . . . . . . . . . .   4
   3.  The Older Registration RFC for NBNs . . . . . . . . . . . . .   5
   4.  Other Existing URN Registrations and RFCs . . . . . . . . . .   5
   5.  Registration Examples . . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   8
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1. Introduction

As a part of the initial development of the Uniform Resource Name (URN) system in the late 1990s, the IETF URN Working Group agreed that it was important to demonstrate that the URN syntax could accommodate existing identifier systems. RFC 2288 [RFC2288] showed the feasibility of using International Standard Book Number (ISBN), International Standard Serial Number (ISSN), and Serial Item and Contribution Identifier (SICI) [ANSI-SICI] as URNs; however, it did not formally register corresponding URN namespaces. This was in part due to the still-evolving process to formalize criteria for namespace definition documents and registration, consolidated later by the IETF into successive Namespace Definition Mechanism documents [RFC2611] [RFC3406].

URN namespaces were subsequently registered for ISBN [RFC3187] and ISSN [RFC3044] as well as for a fairly large collection of other identifiers including National Bibliography Number (NBN) [RFC3188]. The comprehensive list can be found in the IANA Uniform Resource Names (URN) Namespaces registry [IANA-URN] (see also Section 4).

While a URN namespace for SICI could be registered at any time, the SICI standard has not gained broad international acceptance and has not had a namespace defined to date.

The predecessor registration procedure for URN namespaces [RFC3406] required IETF Consensus for formal namespaces. That requirement discouraged some registrations and increased the risk for problems, including use of names without registration ("squatting"). If names are not registered in a consistent way, there is a possibility of the same name being used to identify different namespaces with different rules, resulting in considerable confusion. The requirements have now been changed in RFC 8141 [RFC8141] to adopt a different model that focuses more on encouraging registration of all namespaces that follow the formal namespace syntax, with as much information collected as possible consistent with that goal.

Therefore, this document does the following:

  • Describes the instructions developed with IANA to adapt selected existing registrations to the new model. Those registration updates have been completed for ISBN and ISSN Namespace Identifiers (NIDs) and URN namespaces.
  • Obsoletes the separate RFCs that specify the namespaces for ISSNs and ISBNs to eliminate any ambiguity about the status of new templates and updated registrations.
  • Provides information about the status of NBNs under the new definitions.
  • Provides suggestions to IANA about the handling of other existing registrations not explicitly discussed in this document.

2. Obsoleting Older Registration RFCs for ISSNs and ISBNs

The existing RFCs that describe URN namespaces for ISSNs [RFC3044] and ISBNs [RFC3187] have been identified as "Historic" concurrent with publication of this document. The new registration templates for those namespaces have already been submitted and incorporated into the URN Namespaces registry by IANA.

Those updated templates reflect not only the new template formats but substantive changes to the definitions of the namespaces. The significant changes are summarized in the subsections that follow.

For both ISSN and ISBN namespaces, URN registration practices within them are expected to evolve along with the ISO ISBN and ISSN standards without requiring resubmission of the templates or other formal IETF or IANA URN namespace registration update approval procedures. The subsections that follow clarify the relationship between the original URN namespace registrations for ISBN and ISSN and the recently registered templates that follow the principles of RFC 8141. Approval and registration of those new templates made the older templates obsolete.

2.1. ISBN URN Changes

The revised ISBN namespace reflects the latest version of the ISO ISBN standard, ISO 2108:2017 [ISO-ISBN-b]. The namespace allows for the use of both the old ten-character ISBN numbers described in RFC 3187 and ISO 2108:1992 [ISO-ISBN-a] (formerly known as ISBN-10) and the thirteen-character identifiers introduced in ISO 2108:2005 [ISO-ISBN-c] (formerly known as ISBN-13).

For more details, review the new ISBN registration template and associated documentation [ISBN-Template].

2.2. ISSN URN Changes

The updated ISSN namespace reflects the changes between the current ISSN standard [ISO-ISSN] and its predecessor on which RFC 3044 was based. ISO 3297:2007 introduced the linking ISSN (ISSN-L), which is designated for all media of a serial publication, irrespective of how many there are. Traditional ISSN applies to a single medium only, such as the printed version of a serial.

For more details, review the new ISSN registration template and associated documentation [ISSN-Template].

3. The Older Registration RFC for NBNs

NBN is not a formal international standard or even a single identifier system but an umbrella concept that covers all of the identifier systems the adopting national libraries and their partners use to identify resources that do not have other identifiers. For instance, if a book received via legal deposit does not have an ISBN, the national library gives it a local identifier. The NBN specification provides a simple means of expressing these local identifiers so that they become globally unique URNs, such as urn:nbn:fi-fe19981001.

In addition to the namespace registration itself, RFC 3188 provides some generic information about NBNs and their use and specifies the syntax of URN:NBNs. That syntax guarantees uniqueness by requiring the usage of country codes and institutional identifiers as a part of the Namespace Specific String (NSS). When RFC 3188 is revised, it should be accompanied with a template that revises the registration of the URN:NBN namespace.

4. Other Existing URN Registrations and RFCs

The RFC Series and the IANA URN Namespaces registry contain many URN namespace registrations in addition to those for which this document calls out explicit actions. In general, those existing registrations are still appropriate but omit some information called for in RFC 8141 [RFC8141]. Reregistration with new templates is recommended but not required. Until and unless those registrations are updated as provided for in RFC 8141, the existing registration templates should be read as not requiring or allowing any features that were not allowed and specified by the earlier URN [RFC2141] and registration [RFC3406] specifications.

5. Registration Examples

For examples of registrations using the new model and for information and help in understanding other parts of this document, review the new ISBN and ISSN registration templates [ISBN-Template] [ISSN-Template] and associated documentation in the IANA URN Namespaces registry.

6. IANA Considerations

IANA has completed updates for the registry entries for URN ISSN and ISBN namespaces to reflect the new templates that are compliant with RFC 8141. With respect to namespaces other than those listed above, when registrations and templates are available that conform to the newer rules, they may be substituted for the older ones. However, neither this document nor RFC 8141 supersedes any existing registrations (those for ISBN and ISSN are superseded by the recently registered templates). Therefore, IANA needs to be prepared to maintain a registry whose contents reflect old-style templates for some namespaces and the newer ones for others.

IANA should also note that the portions of the ISBN and ISSN registrations that point to ISO Standards are intended to identify current versions (which may change) rather than only the versions that are active at the time this document is approved (see Section 2). That provision relies on ISO TC 46 and its respective registration authorities to maintain stability of URN references discussed in this document.

7. Security Considerations

While particular URN namespaces and their registrations might conceivably have security implications, this specification merely specifies a transition of a set of namespace registrations and does not have such implications. The security implications associated with particular namespaces are expected to be listed in registration templates as specified in RFC 8141.

8. References

8.1. Normative References

   [RFC8141]  Saint-Andre, P. and J. Klensin, "Uniform Resource Names
              (URNs)", RFC 8141, DOI 10.17487/RFC8141, April 2017,

8.2. Informative References


              ANSI/NISO, "Serial Item and Contribution Identifier
              (SICI)", ANSI/NISO Z39.56-1996 (Version 2), August 1996.

[IANA-URN] IANA, "Uniform Resource Names (URN) Namespaces",



              ISBN International Agency, "Namespace Registration for
              International Standard Book Number (ISBN) ISO 2108:2017",
              June 2017,


              ISO, "Information and documentation - International
              Standard Book Number (ISBN)", ISO 2108:1992, 1992.


              ISO, "Information and documentation - International
              Standard Book Number (ISBN)", ISO 2108:2017, 2017.


              ISO, "Information and documentation - International
              Standard Book Number (ISBN)", ISO 2108:2005, 2005.
   [ISO-ISSN] ISO, "Information and documentation - International
              Standard Serial Number (ISSN)", ISO 3297:2007, 2007.


              ISSN International Centre, "Namespace Registration for
              International Standard Serial Number (ISSN) and Linking
              ISSN (ISSN-L) based on ISO 3297:2007", June 2017,
   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, DOI 10.17487/RFC2141,
              May 1997, <>.
   [RFC2288]  Lynch, C., Preston, C., and R. Daniel, "Using Existing
              Bibliographic Identifiers as Uniform Resource Names",
              RFC 2288, DOI 10.17487/RFC2288, February 1998,
   [RFC2611]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
              "URN Namespace Definition Mechanisms", BCP 33, RFC 2611,
              DOI 10.17487/RFC2611, June 1999,
   [RFC3044]  Rozenfeld, S., "Using The ISSN (International Serial
              Standard Number) as URN (Uniform Resource Names) within an
              ISSN-URN Namespace", RFC 3044, DOI 10.17487/RFC3044,
              January 2001, <>.
   [RFC3187]  Hakala, J. and H. Walravens, "Using International Standard
              Book Numbers as Uniform Resource Names", RFC 3187,
              DOI 10.17487/RFC3187, October 2001,
   [RFC3188]  Hakala, J., "Using National Bibliography Numbers as
              Uniform Resource Names", RFC 3188, DOI 10.17487/RFC3188,
              October 2001, <>.
   [RFC3406]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
              "Uniform Resource Names (URN) Namespace Definition
              Mechanisms", RFC 3406, DOI 10.17487/RFC3406, October 2002,


This document draws heavily on discussions in the IETF URNbis Working Group in the second and third quarters of 2013, particularly during IETF 87 in August 2013, and on informal discussions during the plenary meeting of ISO TC 46 in June 2013. The efforts of those who participated in those discussions are greatly appreciated. It also draws on Internet-Drafts that were developed to update the older registrations before that approach was replaced by the new extended template model. Those documents were prepared by Pierre Godefroy, Juha Hakala, Alfred Hoenes, and Maarit Huttunen.

The current specification benefits significantly from a careful reading and suggestions for editorial changes by Peter Saint-Andre; from considerable work by Stella Griffiths of the ISBN International Agency to refine the ISBN discussion and develop the corresponding template; and from Gaelle Bequet, Pierre Godefroy, and Clement Oury of the ISSN International Centre for similar refinements of the ISSN discussion and template.


Alfred Hoenes was the editor and co-author of two of the documents from which this one is, in part, derived. This document would not have been possible without his contributions.

Authors' Addresses

   John C. Klensin
   1770 Massachusetts Ave, Ste 322
   Cambridge, MA  02140
   United States of America
   Phone: +1 617 245 1457
   Juha Hakala
   The National Library of Finland
   P.O. Box 15, Helsinki University
   Helsinki, MA  FIN-00014