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A Uniform Resource Name (URN) Namespace for Examples

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 6963.
Author Peter Saint-Andre
Last updated 2015-10-14 (Latest revision 2013-04-19)
RFC stream Internet Engineering Task Force (IETF)
Intended RFC status Best Current Practice
Stream WG state (None)
Document shepherd (None)
IESG IESG state Became RFC 6963 (Best Current Practice)
Action Holders
Consensus boilerplate Unknown
Telechat date (None)
Responsible AD Barry Leiba
Send notices to
IANA IANA review state IANA OK - Actions Needed
IANA action state RFC-Ed-Ack
Network Working Group                                     P. Saint-Andre
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Best Current Practice                    April 19, 2013
Expires: October 21, 2013

          A Uniform Resource Name (URN) Namespace for Examples


   This document defines a Uniform Resource Name (URN) namespace
   identifier enabling generation of URNs that are appropriate for use
   in documentation and in URN-related testing and experimentation.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 21, 2013.

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   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

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   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Completed Namespace Definition Template . . . . . . . . . . .   3
   4.  Namespace Considerations  . . . . . . . . . . . . . . . . . .   4
   5.  Community Considerations  . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Appendix A.  Acknowledgements . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The Uniform Resource Name (URN) technology [RFC2141] provides a way
   to generate persistent, location-independent, resource identifiers.
   The primary "scope" of a URN is provided by its namespace identifier
   (NID).  As specified in [RFC3406], there are three kinds of NID:
   formal, informal, and experimental.  Most of the NIDs registered to
   date are formal: as far as is known the few informal namespaces have
   not been widely used, and the experimental namespaces are by
   definition unregistered.

   The experimental namespaces take the form "X-NID" (where "NID" is the
   desired namespace identifier).  Because the "x-" convention has been
   deprecated in general [RFC6648], it seems sensible to achieve the
   same objective in a different way.  Therefore this document registers
   a formal namespace identifier of "example", similar to ""
   and other domain names [RFC2606].  Under the "example" NID,
   specification authors and code developers can mint URNs for use in
   documentation and in URN-related testing and experimentation by
   assigning their own unique namespace-specific strings, without fear
   of conflicts with current or future actual URNs.  Such URNs are
   intended for use as examples in documentation, testing of code for
   URN and URI processing, URN-related experimentation, invalid URNs,
   and other similar uses.  They are not intended for testing non-URI
   code or for building higher-level applications for use over the
   Internet or private networks (e.g., as XML namespace names), since it
   relatively easy to mint URIs whose authority component is a domain
   name controlled by the person or organization that wishes to engage
   in such testing and experimentation.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in

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3.  Completed Namespace Definition Template

3.1.  Namespace ID

   The Namespace ID "example" is requested.

3.2.  Registration Information

   Version 1

   Date: [to be assigned]

3.3.  Declared Registrant of the Namespace

   Registering organization: IETF

   Designated contact: IESG,

3.4.  Declaration of Syntactic Structure

   URNs that use the "example" NID shall have the following structure:


   The Namespace Specific String (NSS) is a mandatory string of ASCII
   characters [RFC20] that conforms to the URN syntax requirements
   [RFC2141] and that provides a name that is useful within the relevant
   documentation example, test suite, or other application.

3.5.  Relevant Ancillary Documentation

   See [RFC6648] for information about deprecation of the "x-"
   convention in protocol parameters and identifiers.

3.6.  Identifier Uniqueness Considerations

   Those who mint example URNs ought to strive for uniqueness in the
   namespace specific string portion of the URN.  However, such
   uniqueness cannot be guaranteed through the assignment process.
   Therefore it is NOT RECOMMENDED for implementers to use example URNs
   for any purposes other than documentation, private testing, and truly
   experimental contexts.

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3.7.  Identifier Persistence Considerations

   Once minted, an example URN is immutable.  However, it is simply a
   string and there is no guarantee that the documentation, test suite,
   or other application using the URN is immutable.

3.8.  Process of Identifier Assignment

   Assignment is completely open, since anyone can mint example URNs for
   use in documentation, private testing, and other experimental

3.9.  Process for Identifier Resolution

   Example URNs are not intended to be resolved, and the namespace will
   probably never be registered with a Resolution Discovery System
   (unless to simply inform requesters that such URNs are merely

3.10.  Rules for Lexical Equivalence

   No special considerations; the rules for lexical equivalence
   specified in [RFC2141] apply.

3.11.  Conformance with URN Syntax

   No special considerations

3.12.  Validation Mechanism


3.13.  Scope

   The scope of an example URN is limited to the documentation in which
   it is found, the test in which it is used, the experiment in which it
   appears, etc.  Example URNs have no meaning outside such strictly-
   limited contexts.

4.  Namespace Considerations

   No existing formal namespace enables entities to generate URNs that
   are appropriate for use as examples in documentation and in URN-
   related testing and experimentation.  It could be argued that no such
   formal namespace is needed, given that experimental namespaces can be
   minted at will.  However, experimental namespaces run afoul of the
   trend away from using the "x-" convention in the names of protocol
   parameters and identifiers [RFC6648].  Additionally, in practice

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   specification authors often mint examples using fake NIDs that go
   unregistered because they are never intended to be used.  To minimize
   the possibility of confusion, use of this dedicated example namespace
   is recommended for generating example URNs.

5.  Community Considerations

   The "example" NID is intended to provide a clean, easily-recognizable
   space for minting examples to be used in documentation and in URN-
   related testing and experimentation.  The Namespace Specific String
   (NSS) is best as a unique string, generated by the person,
   organization, or other entity that creates the documentation, test
   suite, or other application.  There is no issuing authority for
   example URNs and it is not intended that they can be resolved in any
   meaningful way.

   The "example" NID does not obviate the need to coordinate with
   issuing authorities for existing namespaces (e.g., minting
   "urn:example:xmpp:foo" instead of requesting issuance of
   "urn:xmpp:foo"), to register new namespace identifiers if existing
   namespaces do not match one's desired functionality (e.g., minting
   "urn:example:sha-1:29ead03e784b2f636a23ffff95ed12b56e2f2637" instead
   of registering the "sha-1" NID), or to respect the basic spirit of
   URN NID assignment (e.g., setting up shadow NIDs such as
   "urn:example:MyCompany:*" instead of using, say, HTTP URIs).

6.  Security Considerations

   This document introduces no additional security considerations beyond
   those associated with the use and resolution of URNs in general.

7.  IANA Considerations

   This document defines a URN NID registration of "example", to be
   added to the Uniform Resource Names (URN) Formal Namespaces registry.
   The completed registration template can be found in under Section 3.

8.  References

8.1.  Normative References

   [RFC20]    Cerf, V., "ASCII format for network interchange", RFC 20,
              October 1969.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, May 1997.

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   [RFC3406]  Daigle, L., van Gulik, D., Iannella, R., and P. Faltstrom,
              "Uniform Resource Names (URN) Namespace Definition
              Mechanisms", BCP 66, RFC 3406, October 2002.

8.2.  Informative References

   [RFC2606]  Eastlake, D.E. and A. Panitz, "Reserved Top Level DNS
              Names", BCP 32, RFC 2606, June 1999.

   [RFC6648]  Saint-Andre, P., Crocker, D., and M. Nottingham,
              "Deprecating the "X-" Prefix and Similar Constructs in
              Application Protocols", BCP 178, RFC 6648, June 2012.

Appendix A.  Acknowledgements

   Thanks to Martin Duerst, Barry Leiba, and Jim Schaad for their
   feedback, to Christer Holmberg for his Gen-ART review, and to Benoit
   Claise, Adrian Farrel, and Stephen Farrell for their helpful input
   during IESG review.  Julian Reschke inspired the work on this
   document, provided valuable suggestions, and shepherded the document.

Author's Address

   Peter Saint-Andre
   Cisco Systems, Inc.
   1899 Wynkoop Street, Suite 600
   Denver, CO  80202


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