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IETF RFC 6963



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Internet Engineering Task Force (IETF)                    P. Saint-Andre
Request for Comments: 6963                           Cisco Systems, Inc.
BCP: 183                                                        May 2013
Category: Best Current Practice 
ISSN: 2070-1721


          A Uniform Resource Name (URN) Namespace for Examples

 Abstract

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

 Status of This Memo

   This memo documents an Internet Best Current Practice.

   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
   BCPs is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/RFC 6963.

 Copyright Notice

   Copyright (c) 2013 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
   (http://trustee.ietf.org/license-info) 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.








Saint-Andre               Best Current Practice              PAGE 1 top


RFC 6963 Example URNs May 2013 Table of Contents 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 ......................................................6 Appendix A. Acknowledgements .......................................7 1. Introduction The Uniform Resource Name (URN) technology [RFC 2141] 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 [RFC 3406], there are three kinds of NIDs: 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 [RFC 6648], it seems sensible to achieve the same objective in a different way. Therefore, this document registers a formal namespace identifier of "example", similar to "example.com" and other domain names [RFC 2606]. 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 is 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", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119]. Saint-Andre Best Current Practice PAGE 2 top

RFC 6963 Example URNs May 2013 3. Completed Namespace Definition Template 3.1. Namespace ID The Namespace ID "example" has been assigned. 3.2. Registration Information Version 1 Date: 2013-04-24 3.3. Declared Registrant of the Namespace Registering organization: IETF Designated contact: IESG, iesg@ietf.org 3.4. Declaration of Syntactic Structure URNs that use the "example" NID shall have the following structure: urn:example:{NSS} The Namespace Specific String (NSS) is a mandatory string of ASCII characters [RFC 20] that conforms to the URN syntax requirements [RFC 2141] and provides a name that is useful within the relevant documentation example, test suite, or other application. 3.5. Relevant Ancillary Documentation See [RFC 6648] 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. 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. Saint-Andre Best Current Practice PAGE 3 top

RFC 6963 Example URNs May 2013 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 contexts. 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 (except to simply inform requesters that such URNs are merely examples). 3.10. Rules for Lexical Equivalence No special considerations; the rules for lexical equivalence specified in [RFC 2141] apply. 3.11. Conformance with URN Syntax No special considerations 3.12. Validation Mechanism None 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 [RFC 6648]. Additionally, in practice, 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. Saint-Andre Best Current Practice PAGE 4 top

RFC 6963 Example URNs May 2013 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 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", which IANA has added to the "Formal URN Namespaces" registry. The completed registration template can be found in Section 3. Saint-Andre Best Current Practice PAGE 5 top

RFC 6963 Example URNs May 2013 8. References 8.1. Normative References [RFC 20] Cerf, V., "ASCII format for network interchange", RFC 20, October 1969. [RFC 2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC 2141] Moats, R., "URN Syntax", RFC 2141, May 1997. [RFC 3406] 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 [RFC 2606] Eastlake, D. and A. Panitz, "Reserved Top Level DNS Names", BCP 32, RFC 2606, June 1999. [RFC 6648] Saint-Andre, P., Crocker, D., and M. Nottingham, "Deprecating the "X-" Prefix and Similar Constructs in Application Protocols", BCP 178, RFC 6648, June 2012. Saint-Andre Best Current Practice PAGE 6 top

RFC 6963 Example URNs May 2013 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 USA EMail: psaintan@cisco.com Saint-Andre Best Current Practice PAGE 7 top

RFC TOTAL SIZE: 11749 bytes PUBLICATION DATE: Friday, May 24th, 2013 LEGAL RIGHTS: The IETF Trust (see BCP 78)


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