XEP-0277: Microblogging over XMPP

Abstract:This specification defines a method for microblogging over XMPP.
Authors:Peter Saint-Andre, Joe Hildebrand, Valérian Saliou
Copyright:© 1999 - 2011 XMPP Standards Foundation. SEE LEGAL NOTICES.
Status:Experimental
Type:Standards Track
Version:0.2
Last Updated:2011-04-20

WARNING: This Standards-Track document is Experimental. Publication as an XMPP Extension Protocol does not imply approval of this proposal by the XMPP Standards Foundation. Implementation of the protocol described herein is encouraged in exploratory implementations, but production systems are advised to carefully consider whether it is appropriate to deploy implementations of this protocol before it advances to a status of Draft.

Table of Contents


1. Introduction
2. Protocol
    2.1. Location
    2.2. Subscribing to a Microblog
    2.3. Publishing a Post
    2.4. Receiving a Post
    2.5. Replying to a Post
    2.6. Repeating a Post
    2.7. Attaching files to a Post
3. Comments
    3.1. Comments node
    3.2. Adding a comment
4. Message Body
5. Security Considerations
6. IANA Considerations
7. XMPP Registrar Considerations
8. XML Schema
9. Acknowledgements

Appendices
    A: Document Information
    B: Author Information
    C: Legal Notices
    D: Relation to XMPP
    E: Discussion Venue
    F: Requirements Conformance
    G: Notes
    H: Revision History

1. Introduction

Microblogging is an increasingly popular technology for lightweight interaction over the Internet. It differs from traditional blogging in that:

These characteristics map well to instant messaging systems such as those built using Jabber/XMPP technologies (e.g., permissions can be based on existing presence subscriptions as reflected in the XMPP roster or "buddy list"). Furthermore, the push nature of XMPP (especially as formalized in the Personal Eventing Protocol [1] profile of Publish-Subscribe [2] overcomes the problems of polling for updates via HTTP, which has caused scaling issues in existing microblogging services. Therefore this specification defines a method for microblogging over XMPP, building on the existing method for transporting Atom syndication data RFC 4287 [3] over XMPP as described in AtomSub [4]. These XMPP-based methods are complementary to HTTP-based methods, and can provide an XMPP interface to existing microblogging services (which may also be accessible via HTTP, Short Message Service (SMS), and other message transports).

2. Protocol

2.1 Location

A person's microblog SHOULD be located at a personal eventing (PEP) node whose name is "urn:xmpp:microblog:0" but MAY be located at a generic publish-subscribe node that is not attached to a user's IM account. For instance, if the Shakespearean character Romeo has a JabberID of <romeo@montague.lit> then his microblog would be located at that JID with a node of "urn:xmpp:microblog:0". Outside of native XMPP systems, this node can be referred to as the following XMPP URI (the ":" character from the namespace URN is percent-encoded in the query component; see RFC 5122 [5] and RFC 3986 [6]).

xmpp:romeo@montague.lit?;node=urn%3Axmpp%3Amicroblog%3A0

Naturally, this node can be discovered by contacting romeo@montague.lit directly using Service Discovery [7].

2.2 Subscribing to a Microblog

Let us imagine that Juliet wishes to receive the posts that Romeo publishes to his microblog. She has two options:

  1. Implicitly subscribe by advertising support for "urn:xmpp:microblog:0+notify" in her Entity Capabilities [8] data. Romeo's PEP service then automatically sends posts to her when it receives presence from her, until and unless she sends presence of type unavailable or stops advertising an interest in microblog updates.
  2. Explicitly subscribe by sending a formal subscription request to the "urn:xmpp:microblog:0" node at Romeo's JabberID. Romeo's PEP service may send her all posts even if she is offline at the time (depending on service policies regarding presence integration).

2.3 Publishing a Post

Romeo can publish a post via any interface provided by his service, such as a website, the Atom Publishing Protocol (see RFC 5023 [9]), SMS, an IM bot, or XMPP pubsub. Here we assume that the post is provided via XMPP pubsub.

Note: Publishing via HTTP, AtomPub, SMS, or IM bot is simpler for the client (e.g., because the client does not need to generate an Item ID).

Example 1. Publishing a post

<iq from='romeo@montague.lit/pda' 
    id='pub1'
    to='romeo@montague.lit'
    type='set'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='urn:xmpp:microblog:0'>
      <item id='1cb57d9c-1c46-11dd-838c-001143d5d5db'>
        <entry xmlns='http://www.w3.org/2005/Atom'>
          <source>
            <title>Romeo&amp;apos;s Microblog</title>
            <link href='http://montague.lit/romeo'/>
            <id>tag:montague.lit,2008:home</id>
            <updated>2008-05-08T18:30:02Z</updated>
            <author>
              <name>Romeo Montague</name>
              <uri>xmpp:romeo@montague.lit</uri>
            </author>
          </source>
          <title>hanging out at the Caf&amp;#233; Napolitano</title>
          <link rel='alternate'
                type='text/html'
                href='http://montague.lit/romeo/posts/1cb57d9c-1c46-11dd-838c-001143d5d5db'/>
          <link rel='alternate'
                href='xmpp:romeo@montague.lit?;node=urn%3Axmpp%3Amicroblog%3A0;item=1cb57d9c-1c46-11dd-838c-001143d5d5db'/>
          <id>tag:montague.lit,2008-05-08T18:30:02Z:posts-1cb57d9c-1c46-11dd-838c-001143d5d5db</id>
          <published>2008-05-08T18:30:02Z</published>
          <updated>2008-05-08T18:30:02Z</updated>
        </entry>
      </item>
    </publish>
  </pubsub>
</iq>

2.4 Receiving a Post

Because Juliet has sent presence to Romeo including Entity Capabilities data that encapsulates the "urn:xmpp:microblog:0+notify" feature, Romeo's XMPP server will send a PEP notification to Juliet. The notification can include an XMPP message body for backwards-compatibility with Jabber clients that are not pubsub-capable (see Message Body).

Example 2. Receiving a post

<message from='romeo@montague.lit'
         to='juliet@capulet.lit'
         type='headline'>
  <body>hanging out at the Caf&amp;#233; Napolitano</body>
  <event xmlns='http://jabber.org/protocol/pubsub#event'>
    <items node='urn:xmpp:microblog:0'>
      <item id='1cb57d9c-1c46-11dd-838c-001143d5d5db'>
        <entry xmlns='http://www.w3.org/2005/Atom'>
          <source>
            <title>Romeo&amp;apos;s Microblog</title>
            <link href='http://montague.lit/romeo'/>
            <id>tag:montague.lit,2008:home</id>
            <updated>2008-05-08T18:30:02Z</updated>
            <author>
              <name>Romeo Montague</name>
              <uri>xmpp:romeo@montague.lit</uri>
            </author>
          </source>
          <title>hanging out at the Caf&amp;#233; Napolitano</title>
          <link rel='alternate'
                type='text/html'
                href='http://montague.lit/romeo/posts/1cb57d9c-1c46-11dd-838c-001143d5d5db'/>
          <link rel='alternate'
                href='xmpp:romeo@montague.lit?;node=urn%3Axmpp%3Amicroblog%3A0;item=1cb57d9c-1c46-11dd-838c-001143d5d5db'/>
          <id>tag:montague.lit,2008-05-08T18:30:02Z:posts-1cb57d9c-1c46-11dd-838c-001143d5d5db</id>
          <published>2008-05-08T18:30:02Z</published>
          <updated>2008-05-08T18:30:02Z</updated>
        </entry>
      </item>
    </items>
  </event>
</message>

2.5 Replying to a Post

Anyone can publish a post in reply to Romeo's post. Here we assume that a reply comes from Benvolio.

Note: Inclusion of the <in-reply-to/> element defined in RFC 4685 [10] indicates the post to which the user is replying. This reply includes two such elements (one pointing to the HTTP URL for the post and the other pointing to the XMPP URI for the post.

Example 3. Publishing a reply

<iq from='benvolio@montague.lit/mobile' 
    id='uv2x37s5'
    to='benvolio@montague.lit'
    type='set'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='urn:xmpp:microblog:0'>
      <item id='c4145006-1c53-11dd-b2d5-000bcd82471e'>
        <entry xmlns='http://www.w3.org/2005/Atom'
               xmlns:thr='http://purl.org/syndication/thread/1.0'>
          <source>
            <title>Benvolio&amp;apos;s Microblog</title>
            <link href='http://montague.lit/benvolio'/>
            <id>tag:montague.lit,2008:home</id>
            <updated>2008-05-08T18:31:21Z</updated>
            <author>
              <name>Benvolio Montague</name>
              <uri>xmpp:romeo@montague.lit</uri>
            </author>
          </source>
          <title>@romeo cappuccino this late in the day?</title>
          <link rel='alternate'
                type='text/html'
                href='http://montague.lit/benvolio/posts/c4145006-1c53-11dd-b2d5-000bcd82471e'/>
          <link rel='alternate'
                href='xmpp:benvolio@montague.lit?;
                      node=urn%3Axmpp%3Amicroblog%3A0;
                      item=c4145006-1c53-11dd-b2d5-000bcd82471e'/>
          <id>tag:montague.lit,2008-05-08T18:31:21Z:posts-c4145006-1c53-11dd-b2d5-000bcd82471e</id>
          <published>2008-05-08T18:31:21Z</published>
          <updated>2008-05-08T18:31:21Z</updated>
          <thr:in-reply-to
               ref='tag:montague.lit,2008-05-08T18:30:02Z:posts-1cb57d9c-1c46-11dd-838c-001143d5d5db'
               type='application/xhtml+xml'
               href='http://montague.lit/romeo/posts/1cb57d9c-1c46-11dd-838c-001143d5d5db'/>
          <thr:in-reply-to
               ref='tag:montague.lit,2008-05-08T18:30:02Z:posts-1cb57d9c-1c46-11dd-838c-001143d5d5db'
               href='xmpp:romeo@montague.lit?;node=urn%3Axmpp%3Amicroblog%3A0;item=1cb57d9c-1c46-11dd-838c-001143d5d5db'/>
        </entry>
      </item>
    </publish>
  </pubsub>
</iq>

Assuming that Romeo has also shared presence with Benvolio and has advertised support for "urn:xmpp:microblog:0+notify", he will receive the reply that Benvolio sent.

2.6 Repeating a Post

When Benvolio wants to repeat a Romeo's post, his client publishes the same post under a different name. But to be able to track the repeated post original author, Benvolio's client MAY use two specific <author /> child nodes, <name /> and <uri />, containing, respectively, the name of the original post author, and his XMPP URI (JID).

If a comments link is present (see the Comments node section of this document), the client SHOULD repeat it to keep the same discussion about the post.

Example 4. Repeating a Post

<iq from='benvolio@montague.lit/mobile'
    id='pub2'
    to='benvolio@montague.lit'
    type='set'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='urn:xmpp:microblog:0'>
      <item id='1re57d3c-1q46-11dd-748r-024943d2d5rt'>
        <entry xmlns='http://www.w3.org/2005/Atom'>
          <source>
            <title>Benvolio&amp;apos;s Microblog</title>
            <link href='http://montague.lit/benvolio'/>
            <id>tag:montague.lit,2008:home</id>
            <updated>2008-05-08T18:30:02Z</updated>
            <author>
              <name>Romeo Montague</name>
              <uri>xmpp:romeo@montague.lit</uri>
            </author>
          </source>
          <title>hanging out at the Caf&amp;#233; Napolitano</title>
          <link rel='alternate'
                type='text/html'
                href='http://montague.lit/benvolio/posts/1re57d3c-1q46-11dd-748r-024943d2d5rt'/>
          <link rel='alternate'
                href='xmpp:benvolio@montague.lit?;node=urn%3Axmpp%3Amicroblog%3A0;item=1re57d3c-1q46-11dd-748r-024943d2d5rt'/>
          <id>tag:montague.lit,2008-05-08T18:31:21Z:posts-1re57d3c-1q46-11dd-748r-024943d2d5rt</id>
          <published>2008-05-08T18:30:02Z</published>
          <updated>2008-05-08T18:32:02Z</updated>
        </entry>
      </item>
    </publish>
  </pubsub>
</iq>

Thus, a different author JID value lets the client know the microblog item has been repeated from another one.

2.7 Attaching files to a Post

Romeo might want to attach some files, such as pictures of his last vacations, or documents he wants to share. For each file to publish, Romeo's client MUST add a <link /> element. The "href" and "rel" attributes MUST be added; the "title", "type" and "length" ones MIGHT be added.

Example 5. Attaching some files to a Post

<iq from='romeo@montague.lit/pda'
    id='pub3'
    to='romeo@montague.lit'
    type='set'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='urn:xmpp:microblog:0'>
      <item id='1df87v1q-2d12-43se-761w-318790d3g1sq'>
        <entry xmlns='http://www.w3.org/2005/Atom'>
          <source>
            <title>Romeo&amp;apos;s Microblog</title>
            <link href='http://montague.lit/romeo'/>
            <id>tag:montague.lit,2008:home</id>
            <updated>2008-05-08T18:35:02Z</updated>
            <author>
              <name>Romeo Montague</name>
              <uri>xmpp:romeo@montague.lit</uri>
            </author>
          </source>
          <title>Beautiful Eiffel Tower!</title>
          <link rel='alternate'
                type='text/html'
                href='http://montague.lit/romeo/posts/1df87v1q-2d12-43se-761w-318790d3g1sq'/>
          <link rel='alternate'
                href='xmpp:romeo@montague.lit?;node=urn%3Axmpp%3Amicroblog%3A0;item=1df87v1q-2d12-43se-761w-318790d3g1sq'/>
          <link rel='enclosure'
                title='Head in the clouds'
                type='image/jpeg'
                length='156732'
                href='http://montague.lit/romeo/files/uei8327hdz12.jpg'>
               <link xmlns='urn:xmpp:microblog:0'
                     rel='self'
                     title='thumb'
                     type='image/jpeg'
                     length='31723'
                     href='http://montague.lit/romeo/files/uei8327hdz12_thumb.jpg'/>
          </link>
          <link rel='enclosure'
                title='Trip report'
                type='application/pdf'
                length='67123'
                href='http://montague.lit/romeo/files/82he1oh2084s.pdf'/>
          <id>tag:montague.lit,2008-05-08T18:35:02Z:posts-1df87v1q-2d12-43se-761w-318790d3g1sq</id>
          <published>2008-05-08T18:35:02Z</published>
          <updated>2008-05-08T18:35:02Z</updated>
        </entry>
      </item>
    </publish>
  </pubsub>
</iq>

If client can generate some thumbnails images of the attached file (for pictures, videos or documents), it MAY create one or more <link /> sub-elements to the parent file <link /> element. It MUST set "xmlns" attribute to "urn:xmpp:microblog:0"; "rel" attribute to "self"; "title" attribute to "thumb"; "href" to the path of the thumbnail image. It SHOULD also have a "type" attribute specifying the thumbnail file MIME type.

3. Comments

Juliet and Benvolio may want to discuss about latest Romeo's post. Romeo's client MIGHT add a element to the PubSub item. The element MUST have "rel", "title" and "href" attributes, where "rel" MUST have the "related" value; "title" MUST have the "comments" value; "href" MUST be an XMPP URI (see RFC 5122 [11] and RFC 3986 [12]).

3.1 Comments node

We assume Romeo's client first created a comments node (named "urn:xmpp:microblog:0:comments:hash", where "hash" is a client-side generated random hash), with defaults "pubsub#access_model" and "pubsub#publish_model" privacy settings (see Publish-Subscribe [13] for node creation and configuration).

Example 6. Adding a comments link to a Post

<iq from='romeo@montague.lit/pda'
    id='pub4'
    to='romeo@montague.lit'
    type='set'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='urn:xmpp:microblog:0'>
      <item id='2ze57d9c-1c46-21df-830c-002143d3d2qgf'>
        <entry xmlns='http://www.w3.org/2005/Atom'>
          <source>
            <title>Romeo&amp;apos;s Microblog</title>
            <link href='http://montague.lit/romeo'/>
            <id>tag:montague.lit,2008:home</id>
            <updated>2008-05-08T18:30:02Z</updated>
            <author>
              <name>Romeo Montague</name>
              <uri>xmpp:romeo@montague.lit</uri>
            </author>
          </source>
          <title>hanging out at the Caf&amp;#233; Napolitano</title>
          <link rel='alternate'
                type='text/html'
                href='http://montague.lit/romeo/posts/2ze57d9c-1c46-21df-830c-002143d3d2qgf'/>
          <link rel='alternate'
                href='xmpp:romeo@montague.lit?;node=urn%3Axmpp%3Amicroblog%3A0;item=2ze57d9c-1c46-21df-830c-002143d3d2qgf'/>
          <link rel='related'
                title='comments'
                href='xmpp:romeo@montague.lit?;node=urn%3Axmpp%3Amicroblog%3A0%3Acomments%3Add88c9bc58886fce0049ed050df0c5f2'/>
          <id>tag:montague.lit,2008-05-08T18:38:02Z:posts-2ze57d9c-1c46-21df-830c-002143d3d2qgf</id>
          <published>2008-05-08T18:38:02Z</published>
          <updated>2008-05-08T18:38:02Z</updated>
        </entry>
      </item>
    </publish>
  </pubsub>
</iq>

3.2 Adding a comment

If Juliet wants to comment Romeo's latest post, her client MUST then send a new Atom entry to the defined PubSub node.

Example 7. Adding a comment to a comments node

<iq from='juliet@capulet.lit/pc'
    id='comment1'
    to='juliet@capulet.lit'
    type='set'>
  <pubsub xmlns='http://jabber.org/protocol/pubsub'>
    <publish node='urn:xmpp:microblog:0:comments:dd88c9bc58886fce0049ed050df0c5f2'>
      <item id='b2106a80de39ef5ec6b8f7b69cb610c2'>
        <entry xmlns='http://www.w3.org/2005/Atom'>
          <source>
            <author>
              <name>Juliet Capulet</name>
              <uri>xmpp:juliet@capulet.lit</uri>
            </author>
          </source>
          <title>She is so pretty!</title>
          <published>2008-05-08T18:39:02Z</published>
        </entry>
      </item>
    </publish>
  </pubsub>
</iq>

If Benvolio wants to retrieve the comments node, his client will send a standard PubSub stanza to request all items (see Publish-Subscribe [14] for all items retrieving).

4. Message Body

Depending on service policies and the value of the "pubsub#include_body" node configuration option, microblogging notifications SHOULD include a message <body/> element for backwards-compatibility with Jabber clients that are not pubsub-capable. It is RECOMMENDED for the XML character value of the <body/> element to be the same as that of the <title/> child of the Atom <entry/>.

5. Security Considerations

This specification does not introduce new security concerns above and beyond those already discussed in the specifications on which it depends.

6. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [15].

7. XMPP Registrar Considerations

The XMPP Registrar [16] is requested to issue an initial namespace of "urn:xmpp:microblog:0".

8. XML Schema

This specification re-uses the schema for the Atom content format, i.e., the 'http://www.w3.org/2005/Atom' namespace (see RFC 4287).

9. Acknowledgements

Thanks to Ralph Meijer and Paul Scott for their suggestions.

Appendices

Appendix A: Document Information

Series: XEP
Number: 0277
Publisher: XMPP Standards Foundation
Status: Experimental
Type: Standards Track
Version: 0.2
Last Updated: 2011-04-20
Approving Body: XMPP Council
Dependencies: None
Supersedes: None
Superseded By: None
Short Name: NOT YET ASSIGNED
Source Control: HTML  RSS
This document in other formats: XML  PDF

Appendix B: Author Information

Peter Saint-Andre

Email: stpeter@jabber.org
JabberID: stpeter@jabber.org
URI: https://stpeter.im/

Joe Hildebrand

Email: jhildebr@cisco.com
JabberID: hildjj@jabber.org

Valérian Saliou

Email: vanaryon@gmail.com
JabberID: vanaryon@jappix.com
URI: http://vanaryon.eu/

Appendix C: Legal Notices

Copyright

This XMPP Extension Protocol is copyright © 1999 - 2011 by the XMPP Standards Foundation (XSF).

Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <http://xmpp.org/extensions/ipr-policy.shtml> or obtained by writing to XMPP Standards Foundation, 1899 Wynkoop Street, Suite 600, Denver, CO 80202 USA).

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.

Errata can be sent to <editor@xmpp.org>.

Appendix F: Requirements Conformance

The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

Appendix G: Notes

1. XEP-0163: Personal Eventing Protocol <http://xmpp.org/extensions/xep-0163.html>.

2. XEP-0060: Publish-Subscribe <http://xmpp.org/extensions/xep-0060.html>.

3. RFC 4287: The Atom Syndication Format <http://tools.ietf.org/html/rfc4287>.

4. Atomsub: Transporting Atom Notifications over the Publish-Subscribe Extension to the Extensible Messaging and Presence Protocol (XMPP) <http://xmpp.org/internet-drafts/draft-saintandre-atompub-notify-07.html>. Work in progress.

5. RFC 5122: Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP) <http://tools.ietf.org/html/rfc5122>.

6. RFC 3986: Uniform Resource Identifiers (URI): Generic Syntax <http://tools.ietf.org/html/rfc3986>.

7. XEP-0030: Service Discovery <http://xmpp.org/extensions/xep-0030.html>.

8. XEP-0115: Entity Capabilities <http://xmpp.org/extensions/xep-0115.html>.

9. RFC 5023: The Atom Publishing Protocol <http://tools.ietf.org/html/rfc5023>.

10. RFC 4685: Atom Threading Extensions <http://tools.ietf.org/html/rfc4685>.

11. RFC 5122: Internationalized Resource Identifiers (IRIs) and Uniform Resource Identifiers (URIs) for the Extensible Messaging and Presence Protocol (XMPP) <http://tools.ietf.org/html/rfc5122>.

12. RFC 3986: Uniform Resource Identifiers (URI): Generic Syntax <http://tools.ietf.org/html/rfc3986>.

13. XEP-0060: Publish-Subscribe <http://xmpp.org/extensions/xep-0060.html>.

14. XEP-0060: Publish-Subscribe <http://xmpp.org/extensions/xep-0060.html>.

15. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.

16. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <http://xmpp.org/registrar/>.

Appendix H: Revision History

Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/

Version 0.2 (2011-04-20)

Added file attachment and commenting features; updated XML namespaces in examples.

(vs)

Version 0.1 (2010-01-27)

Initial version as accepted for publication by the XMPP Council.

(psa)

Version 0.0.1 (2008-05-07)

First draft.

(psa/jh)

END