Internet Engineering Task Force (IETF) J. Klensin
Request for Comments: 8254
Obsoletes: 3044, 3187 J. Hakala
Category: Standards Track The National Library of Finland
ISSN: 2070-1721 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and ISBN namespaces, which are now outdated because the descriptions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
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]
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:
o 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.
o 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.
o Provides information about the status of NBNs under the new
o 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
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
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
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.
8.1. 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",
[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, <https://www.rfc-editor.org/info/rfc3188>.
[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.
John C. Klensin
1770 Massachusetts Ave, Ste 322
Cambridge, MA 02140
United States of America
Phone: +1 617 245 1457
The National Library of Finland
P.O. Box 15, Helsinki University
Helsinki, MA FIN-00014