XEP-0277: Microblogging over XMPP

2.1 Location¶

A person's microblog SHOULD be located at a personal eventing (PEP) node named "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 (see XEP-0060 § 12.21).

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

Note that the ":" character from the namespace URN is percent-encoded in the query component (see RFC 5122 [5] and RFC 3986 [6]).

Naturally, this node can be discovered by contacting romeo@montague.lit directly using Service Discovery (XEP-0030) [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 (XEP-0115) [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.

The post content itself can be either text (content element without "type" attribute or with "type" attribute with "text" value) or XHTML ("content" element "type" attribute with "xhtml" value). If Romeo publishes XHTML content, his client MUST publish two "content" elements: a text one, and a XHTML one. For XHTML publishing, see Publish-Subscribe (XEP-0060) [2].

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).

<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'>
          <title type='text'>hanging out at the Caf&#233; Napolitano</title>
          <id>tag:montague.lit,2008-05-08: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>

Note: The "title" element is required to be included in an "atom:entry" element according to RFC 4287 [3]. An implementation MAY provide also "atom:summary" and/or "atom:content" elements too if it needs.

<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'>
          <title type='xhtml'>
            <div xmlns="http://www.w3.org/1999/xhtml">
              <p>hanging out at the <strong>Caf&#233; Napolitano</strong></p>
            </div>
          </title>
          <id>tag:montague.lit,2008-05-08:posts-1cb57d9c-1c46-11dd-838c-001143d5d5db</id>
          <published>2008-05-08T18:30:02Z</published>
          <updated>2008-05-08T18:30:02Z</updated>
          <generator uri='https://capu.chat' version='42'>CapuChat</generator>
        </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).

<message from='romeo@montague.lit'
         to='juliet@capulet.lit'
         type='headline'>
  <body>hanging out at the Caf&#233; Napolitano</body>
  <event xmlns='http://jabber.org/protocol/pubsub#event'>
    <items node='urn:xmpp:microblog:0'>
      <item id='1cb57d9c-1c46-11dd-838c-001143d5d5db' publisher='romeo@montague.lit'>
        <entry xmlns='http://www.w3.org/2005/Atom'>
          <title type='text'>hanging out at the Caf&#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,2008-05-08:posts-1cb57d9c-1c46-11dd-838c-001143d5d5db</id>
          <published>2008-05-08T18:30:02Z</published>
          <updated>2008-05-08T18:30:02Z</updated>
          <generator uri='https://capu.chat' version='42'>CapuChat</generator>
        </entry>
      </item>
    </items>
  </event>
</message>

Note: these alternate links were not posted by the original client because clients can't compute them themselves. These things SHOULD be inserted at server side though.

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 "thr:in-reply-to" element defined in RFC 4685 [11] 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.

Note: The post can be a reply to more than the only one another.

<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'>
          <author>
            <name>Benvolio Montague</name>
            <uri>xmpp:romeo@montague.lit</uri>
          </author>
          <title type='text'>@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,2008-05-08: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,2008-05-08: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,2008-05-08: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 specific "atom:author" child node, "atom:name" and "atom:uri", containing, respectively, the name of the original post author, and his XMPP URI (JID).

If a comments link is present (see the Post Comments section of this document), the client SHOULD repeat it to keep the same discussion about the post. The client also MAY create a separate node to discuss and specify it or specify both.

The client SHOULD also put an "atom:link" element with "rel" attribute set to "via" and point it to the original 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'>
          <author>
            <name>Romeo Montague</name>
            <uri>xmpp:romeo@montague.lit</uri>
          </author>
          <title type='text'>hanging out at the Caf&#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'/>
          <link rel='via'
                href='xmpp:romeo@montague.lit?;node=urn%3Axmpp%3Amicroblog%3A0;item=1cb57d9c-1c46-11dd-838c-001143d5d5db'
                ref='tag:montague.lit,2008-05-08:posts-1cb57d9c-1c46-11dd-838c-001143d5d5db'/>
          <id>tag:montague.lit,2008-05-08: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.

It's also possible for Benvolio to add his own thougths to the repost. To do this he SHOULD wrap the original content in the "xhtml:blockquote" element and after it add his own content. Also, the client MAY post reply without quotation to the original thread to inform users about the repost.

2.7 Post Categories¶

It's often handy to specify categories (or tags) to a post to make it easier to find it or to structure a blog. It's possible by adding "atom:category" element to the entry (it can be blog or replies entry).

<entry xmlns='http://www.w3.org/2005/Atom'>
  ...
  <category term='humour'/>
  <category term='xmpp'/>
  ...
</entry>

3.1 Post Comments¶

We assume Romeo's client first created a comments node (named "urn:xmpp:microblog:0:comments/ID", where "ID" is the microblog item ID, or the SHA-1 encoded attachment URI, as defined in RFC 3174 [12]).

<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'>
          <title type='text'>hanging out at the Caf&#233; Napolitano</title>
          <link rel='replies'
                title='comments'
                href='xmpp:pubsub.montague.lit?;node=urn%3Axmpp%3Amicroblog%3A0%3Acomments%2Fdd88c9bc58886fce0049ed050df0c5f2'/>
          <id>tag:montague.lit,2008-05-08: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 sends a new Atom entry to the defined PubSub node.

Note: A comments node SHOULD be located at a generic publish-subscribe node that is not attached to a user's IM account, but MAY be located at a personal eventing (PEP) node.

<iq from='juliet@capulet.lit/pc'
    id='comment1'
    to='pubsub.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'>
          <author>
            <name>Juliet Capulet</name>
            <uri>xmpp:juliet@capulet.lit</uri>
          </author>
          <title type='text'>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 (XEP-0060) [2] for all items retrieving).

4.1 Microblog node configuration¶

Here are recommendations for a microblogging node (usually located at PEP and named by the "urn:xmpp:microblog:0" namespace) configuration:

1. The "pubsub#notify_retract" MUST be set to true to provide clients the ability to track if some items were retracted and reflect such changes in the UI correctly.
2. The "pubsub#max_items" SHOULD be increased from the default value to some reasonable value.
3. The "pubsub#send_last_published_item" SHOULD be changed to "never".

4.2 Comments node configuration¶

Here are recommendations for a comments node configuration:

1. The "pubsub#notify_retract" MUST be set to true to provide clients the ability to track if some items were retracted and reflect such changes in the UI correctly.
2. The "pubsub#max_items" SHOULD be increased from the default value to some reasonable value.
3. The "pubsub#access_model" SHOULD be set to "open" to allow any user to comment to a post. Other values are suitable too according to the user's settings.

7.1 Pubsub Item ID vs. Atom Entry id¶

There are two different things that carry a similar sense: the XMPP pubsub Item ID and the "atom:id" element. This section is devoted to make a separation between them.

The pubsub Item ID MUST be used when linking to an entry with an XMPP channel (i.e. by including it in the URI with the "xmpp" schema). the Atom entry ID MUST be built according to RFC 4287 [3] and used in aggregators with the aim of revealing of post duplicates, reposts, mentions, syndications, etc.

Note that the rules of comparing, building and security notes for "atom:id" are listed in the RFC 4287 [3].

7.2 Aggregator Usecases¶

9.1 Comment Author¶

The client SHOULD check that the comment author information (provided in the "author" element) is valid, by checking that the "publisher" item attribute value matches the "uri" element value. If there is a difference or the check can not be performed because there was not a "publisher" attribute included, the comment can be displayed, but it is RECOMMENDED to specify there is a security problem.

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

2. XEP-0060: Publish-Subscribe <https://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) <https://tools.ietf.org/html/draft-saintandre-atompub-notify-07>. 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 <https://xmpp.org/extensions/xep-0030.html>.

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

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

10. XEP-0071: XHTML-IM <https://xmpp.org/extensions/xep-0071.html>.

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

12. RFC 3174: US Secure Hash Algorithm 1 (SHA1) <http://tools.ietf.org/html/rfc3174>.

13. XEP-0080: User Geolocation <https://xmpp.org/extensions/xep-0080.html>.

14. 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/>.

15. 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 <https://xmpp.org/registrar/>.