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 (XEP-0163)  profile of Publish-Subscribe (XEP-0060) ) 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  over XMPP as described in AtomSub . 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 messaging transports).
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 <firstname.lastname@example.org> 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).
Let us imagine that Juliet wishes to receive the posts that Romeo publishes to his microblog. She has two options:
Romeo can publish a post via any interface provided by his service, such as a website, the Atom Publishing Protocol (see RFC 5023 ), 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) .
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).
Note: The "title" element is required to be included in an "atom:entry" element according to RFC 4287 . An implementation MAY provide also "atom:summary" and/or "atom:content" elements too if it needs.
It's possible to insert some rich content in the post or comment. It can be some text formatting, images, etc. Only "xhtml" content type is supported for the moment by this document but possibly it will be extended later. Also, it is RECOMMENDED for the client to restrict XHTML content to the XHTML-IM subset (XHTML-IM (XEP-0071) ).
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).
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.
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  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.
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.
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.
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.
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).
Juliet and Benvolio may want to discuss about latest Romeo's post. To enable this, Romeo's client MAY add a "atom:link" element to the PubSub item. The element MUST have "rel", "title" and "href" attributes, where "rel" MUST have the "replies" value; "title" MUST have the "comments" value; "href" MUST be an XMPP URI (see RFC 5122  and RFC 3986 ).
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 ).
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.
We have described two pubsub nodes types here: the one is for the microblog itself and the other one is for comments to posts.
Usage specific requires the special parameters to these nodes to be specified. This section describes recommendation for them.
Here are recommendations for a microblogging node (usually located at PEP and named by the "urn:xmpp:microblog:0" namespace) configuration:
Here are recommendations for a comments node configuration:
In order to provide users with some metadata (i.e. blog title or author information) about the microblog, the client MUST add an item with such information. The client MUST set the ID of the item to "0".
It also necessary to link a comments node to the post which discussed in the node. We will do it by adding the "atom:link" element with "rel=start" attribute:
Juliet may want to know which places are Romeo's notices related to. That's why Romeo's client MAY geotag microblog entries, using the User Geolocation (XEP-0080)  protocol for storing geolocation information.
Romeo's client MUST create a "geoloc" element, with the User Geolocation (XEP-0080)  reference namespace: "http://jabber.org/protocol/geoloc".
In order to provide some statistical information, to represent the blogs other ways than XMPP (i.e. in web or NNTP), we will need other entities called "Aggregators".
You can think of aggregators like about search engines in the web: they gather information from the whole web and then represent it suitable ways. The same is true here: Aggregators just subscibe to many entities and then they can build a database to make queries and show appropriate information according to these queries. Also they can be used to represent information in web or other networks.
Unlike web search engines, an XMPP aggregator does not need to gather information by downloading it frequently to check if something was changed. Instead, it can listen to pubsub events and make its database up-to-date based on this information.
Aggregators can be started by different people with different aims. It can be aggregator which devoted to the concrete blog service provider which will be subscribed only to its own users, or it can be a global search engine which tries to subscribe to most of users or to aggregate the feeds of other aggregators.
This section will describe most used aggregator usecases but the list is not exhaustive.
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  and used in aggregators with the aim of revealing of post duplicates, reposts, mentions, syndications, etc.
One of the possible aims of aggregator services is to provide web representaion of blogs.
TBD: insert alternate link to the post with the http address of the post.
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 "atom:title" child of the "atom:entry".
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.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) .
The XMPP Registrar  is requested to issue an initial namespace of "urn:xmpp:microblog:0".
This specification re-uses the schema for the Atom content format, i.e., the 'http://www.w3.org/2005/Atom' namespace (see RFC 4287).
Thanks to Ralph Meijer and Paul Scott for their suggestions.
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The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) 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.
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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".
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.
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/>.
Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/
Updated contact information for Valerian Saliou
Added node configuration suggestions; removed file attachments; added rich content examples; change atom:content to atom:title anywhere in the document; invented the "Aggregator" entity; changed nodes metainformation locations; added possibility to add own content to repost.
Changed the commenting Pubsub service from PEP to external.
Added microblog metadata feature, ID innacurracy fixed, urn:xmpp:inbox support added, new commenting namespaces, first comment marker, security considerations added.
Comments link "link[rel=related]" is now "link[rel=replies]" and "title" is now "content[type=text]" or "content[type=xhtml]"; added geolocation feature; added commenting feature on attachments.
Added file attachment and commenting features; updated XML namespaces in examples.
Initial version as accepted for publication by the XMPP Council.