Network Working Group                                     P. Saint-Andre
Request for Comments: 4854                                           XSF
Category: Informational                                       April 2007


              A Uniform Resource Name (URN) Namespace for
  Extensions to the Extensible Messaging and Presence Protocol (XMPP)

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   This document describes a Uniform Resource Name (URN) namespace for
   uniquely identifying Extensible Markup Language (XML) formats and
   protocols that provide extensions to the Extensible Messaging and
   Presence Protocol (XMPP) and are defined in specifications published
   by the XMPP Standards Foundation (XSF).

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Specification Template  . . . . . . . . . . . . . . . . . . . . 3
   3.  Namespace Considerations  . . . . . . . . . . . . . . . . . . . 6
   4.  Community Considerations  . . . . . . . . . . . . . . . . . . . 6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     7.1.  Normative References  . . . . . . . . . . . . . . . . . . . 8
     7.2.  Informative References  . . . . . . . . . . . . . . . . . . 8

1.  Introduction

   While the Extensible Messaging and Presence Protocol (XMPP), as
   specified in [XMPP-CORE] and [XMPP-IM], provides basic messaging and
   presence functionality, the fact that XMPP is at root a technology
   for streaming Extensible Markup Language [XML] data makes it possible
   to include virtually any structured information within XMPP, as long
   as such information is qualified by appropriate XML namespaces
   [XML-NAMES].  When sent over XMPP, such structured data formats and
   protocols are generally referred to as "XMPP extensions".

   A large number of such XMPP extensions exist.  The main standards
   development organization in which such extensions are defined is the
   XMPP Standards Foundation (XSF) (formerly the Jabber Software
   Foundation), which contributed XMPP to the Internet Standards
   process.  Typically, such extensions are defined within the XSF's
   XMPP Extension Protocol (XEP) specification series.  To date, the XML
   namespaces defined within the Jabber/XMPP community have used names
   of the form "jabber:*" (deprecated since early 2002) and
   "http://jabber.org/protocol/*" (not including names of the form
   "urn:ietf:params:xml:ns:xmpp-*" specified in the XMPP RFCs).
   However, it is desirable that names associated with future XMPP
   extensions be both unique and persistent, which is not necessarily
   the case with names that are also HTTP URLs.  Therefore, in
   accordance with the process defined in [MECHANISMS], this document
   registers a formal namespace identifier (NID) for Uniform Resource
   Names [URN] associated with XMPP extensions published in the XSF's
   XEP series and for XML namespaces registered with the XSF's XMPP
   Registrar function [REGISTRAR].

2.  Specification Template

   Namespace ID:

      The Namespace ID "xmpp" is requested.

   Registration Information:

      Version 1
      Date: 2007-04-27

   Declared Registrant of the Namespace:

      Registering organization
         Organization: XMPP Standards Foundation
         Address: P.O. Box 1641, Denver, CO 80201 USA

      Designated contact
         Role: XMPP Registrar
         Email: registrar@xmpp.org

   Declaration of Syntactic Structure:

      The Namespace Specific String (NSS) of all URNs that use the
      "xmpp" NID shall have the following structure:

         urn:xmpp:{ShortName}:{SubName}

      The keywords have the following meaning:

         (1) the "ShortName" is a required US-ASCII string that
         conforms to the URN syntax requirements (see RFC 2141)
         and defines a particular protocol or format that is used
         as an XMPP extension.

         (2) the "SubName" is an optional US-ASCII string that
         conforms to the URN syntax requirements (see RFC 2141)
         and defines a particular subset of the relevant protocol
         or format.

      The XSF's XMPP Registrar function shall be responsible for
      managing the assignment of both "ShortName" and "SubName"
      strings and maintaining a registry of resulting namespaces
      at <http://www.xmpp.org/registrar/namespaces.html>.  The
      XMPP Registrar may also assign URNs in sub-trees below the
      level of the ShortName or SubName as needed for use in various
      XMPP extensions.

   Relevant Ancillary Documentation:

      Information about the XSF's XMPP Registrar function can be
      found at <http://www.xmpp.org/extensions/xep-0053.html>
      and <http://www.xmpp.org/registrar/>.

   Identifier Uniqueness Considerations:

      The XMPP Registrar is already responsible for managing
      the assignment of XML namespace names of the form
      "http://jabber.org/protocol/{ShortName}" and
      "http://jabber.org/protocol/{ShortName}#{SubName}"
      (e.g., "http://jabber.org/protocol/pubsub" and
      "http://jabber.org/protocol/disco#info").  In order to
      assign namespace names in the context of the "xmpp"
      NID, the XMPP Registrar shall simply modify the syntax
      of the namespace names it assigns from

      "http://jabber.org/protocol/{ShortName}" and
      "http://jabber.org/protocol/{ShortName}#{SubName}" to
      "urn:xmpp:{ShortName}" and "urn:xmpp:{ShortName}:{SubName}".

      The XMPP Registrar shall ensure the uniqueness of all
      XMPP URNs by checking such names against the list of
      existing namespace names, as documented in XEP-0053
      (the controlling specification for the XMPP Registrar
      function).  The XMPP Registrar shall, in all cases, directly
      ensure the uniqueness of the assigned strings and shall
      not assign secondary responsibility for management of any
      sub-trees.  However, the XMPP Registrar may assign URNs
      in sub-trees below the level of the ShortName or SubName
      as needed for use in various XMPP extensions.  The
      resulting URNs shall not be re-assigned.

   Identifier Persistence Considerations:

      The XMPP Registrar shall provide clear documentation of
      the registered uses of the "xmpp" NID in the form of
      XMPP Extension Protocol (XEP) specifications published
      at <http://www.xmpp.org/extensions/>, as well as a
      registry of the namespace names themselves at
      <http://www.xmpp.org/registrar/namespaces.html>.

   Process of Identifier Assignment:

      The XMPP Registrar's processes and procedures for
      identifier assignment are documented in XEP-0053,
      which is the controlling specification for the XMPP
      Registrar function.  In particular, identifiers shall
      be issued only upon advancement of the relevant protocol
      specification to a status of Draft within the standards
      process, followed by the XMPP Standards Foundation (as
      specified in XEP-0001).  The XMPP Registrar shall check
      all identifiers against the list of existing namespace
      names to ensure uniqueness and to encourage relevance
      and memorability.  Assignment of URNs within the "xmpp"
      tree is reserved to the XMPP Standards Foundation,
      specifically to its XMPP Registrar function.

   Process for Identifier Resolution:

      The namespace is not currently listed with a Resolution
      Discovery System (RDS), but nothing about the namespace
      prohibits the future definition of appropriate resolution
      methods or listing with an RDS.

   Rules for Lexical Equivalence:

      No special considerations; the rules for lexical
      equivalence specified in RFC 2141 apply.

   Conformance with URN Syntax:

      No special considerations.

   Validation Mechanism:

      None specified.

   Scope:

      Global.

3.  Namespace Considerations

   The XMPP Standards Foundation has been developing Internet protocols
   since August 2001 and that work is expected to continue for the
   foreseeable future.  The old-style "jabber:*" namespace names
   originally used in the Jabber open-source community were not proper
   URNs or URIs and thus were deprecated in early 2002.  Since then, the
   namespace names assigned by the XMPP Registrar function of the XMPP
   Standards Foundation have been (equivalent to) specialized HTTP URLs
   whose authority component is "jabber.org".  While that domain is
   currently under the control of the XMPP Standards Foundation, there
   is no guarantee that it will always remain so, thus potentially
   threatening the reliability and permanence of the assigned namespace
   names.  The use of Uniform Resource Names with an appropriate
   Namespace ID will enable the XMPP Standards Foundation to assign
   cleaner, more general, more permanent, more reliable, and more
   controllable namespace names related to the XMPP extensions it
   defines, while keeping the tree of XMPP extensions produced by the
   XMPP Standards Foundation properly separate from the IETF tree used
   to define some of the core XMPP namespaces as well as namespaces
   related to XMPP extensions that may be produced in the future by the
   IETF.

4.  Community Considerations

   The XMPP standards development community will benefit from
   publication of this namespace by having more permanent and reliable
   names for the XML namespaces defined in XMPP Extension Protocol
   specifications produced by the XMPP Standards Foundation.

   The standards process followed by the XSF is open to contributions
   from any interested individual; such a contribution takes the form of
   a proposal submitted to the XMPP Extensions Editor
   <mailto:editor@xmpp.org>, accepted by the XMPP Council
   <http://www.xmpp.org/council/>, and published in the XSF's XMPP
   Extension Protocol (XEP) series at <http://www.xmpp.org/extensions/>.
   Use of the proposed space for a particular XML format or protocol
   extension will be contingent upon advancement of the appropriate
   specification within the XSF's standards process (as documented in
   [XEP]) and issuance of a namespace name within the "xmpp" tree by the
   XMPP Registrar (as documented in [REGISTRAR]).

5.  Security Considerations

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

6.  IANA Considerations

   This document defines a URN NID registration of "xmpp", which has
   been entered into the IANA registry located at
   <http://www.iana.org/assignments/urn-namespaces>.

7.  References

7.1.  Normative References

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

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

7.2.  Informative References

   [REGISTRAR]   Saint-Andre, P., "XMPP Registrar Function", XSF
                 XEP 0053, December 2006.

   [XEP]         Saint-Andre, P., "XMPP Extension Protocols", XSF
                 XEP 0001, December 2006.

   [XML]         Bray, T., Paoli, J., Sperberg-McQueen, C., and E.
                 Maler, "Extensible Markup Language (XML) 1.0 (2nd ed)",
                 W3C REC-xml, October 2000,
                 <http://www.w3.org/TR/REC-xml>.

   [XML-NAMES]   Bray, T., Hollander, D., and A. Layman, "Namespaces in
                 XML", W3C REC-xml-names, January 1999,
                 <http://www.w3.org/TR/REC-xml-names>.

   [XMPP-CORE]   Saint-Andre, P., "Extensible Messaging and Presence
                 Protocol (XMPP): Core", RFC 3920, October 2004.

   [XMPP-IM]     Saint-Andre, P., "Extensible Messaging and Presence
                 Protocol (XMPP): Instant Messaging and Presence",
                 RFC 3921, October 2004.

Author's Address

   Peter Saint-Andre
   XMPP Standards Foundation
   P.O. Box 1641
   Denver, CO  80201
   USA

   EMail: stpeter@jabber.org
   URI:   xmpp:stpeter@jabber.org

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