XEP-0036: Pub-Sub Subscriptions

A proposal for the subscribe half of a publish-subscribe protocol within Jabber.

WARNING: This document has been retracted by the author(s). Implementation of the protocol described herein is not recommended. Developers desiring similar functionality should implement the protocol that supersedes this one (if any).

Document Information

Author Information

Peter Millard

See Author Note

Peter Saint-Andre

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

Legal Notices

Copyright

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.

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## 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. In no event shall the XMPP Standards Foundation or the authors of this Specification be liable for any claim, damages, or other liability, whether in an action of contract, tort, or otherwise, arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification. ##

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IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which may be found at <http://www.xmpp.org/extensions/ipr-policy.shtml> or obtained by writing to XSF, P.O. Box 1641, Denver, CO 80201 USA).

Discussion Venue

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.

Conformance Terms

The following 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".

1. Introduction
2. Narrative
3. Protocol Details
4. Author Note
Notes
Revision History

1. Introduction

The Jabber community needs a cohesive standard for publish-subscribe functionality. Certainly there is interest in developing such a standard, as witness the number of proposals written on this topic (Jabber Event Notification Service [1], Publish/Subscribe [2], XEP-0028). Unfortunately, past discussion of this issue has been clouded by confusion over requirements and even terminology. This XEP seeks to clarify the situation somewhat and to provide a protocol for the subscribe half of publish-subscribe functionality within Jabber.

2. Narrative

Traditional pub-sub consists of event notification. This makes it possible for entities to publish data and for other interested entities to receive notification when the data is published. The following are some likely applications of pub-sub functionality within Jabber:

In such systems, a subscriber would request to receive notifications about data the subscriber is interested in. We define a "topic" as an object that defines the relationship between a publisher and its subscribers. Specifically, a topic contains three essential collections of information:

We define an "item" as an instance of data published by the publisher that fits the description associated with a topic. Each item MAY possess a unique identifier that enables the data to be tracked. (NOTE: This XEP does not address the durability of items, i.e., data storage.)

A topic is addressed by means of a unique "topic ID". A topic ID is simply a string with no required semantic meaning. While a topic ID may have semantic meaning (e.g., '/instruments/guitars/electric' or 'rec.music.dylan'), such meaning is not necessary and a topic ID may be any random string (e.g., 'a1gh83jfn342092'). The only requirement is that a topic ID be unique within the context of a specific pub-sub domain (e.g., pubsub.jabber.org).

3. Protocol Details

<iq type="set" from="pgm@jabber.org" to="pubsub.jabber.org" id="1">
    <query xmlns="jabber:iq:pubsub">
        <subscribe>
            <topic id="12345"/>
            <topic id="/presence/dizzyd@jabber.org"/>
        </subscribe>
    </query>
</iq>

<iq type="set" from="pgm@jabber.org" to="pubsub.jabber.org" id="1">
    <query xmlns="jabber:iq:pubsub">
        <unsubscribe>
            <topic id="12345"/>
        </unsubscribe>
    </query>
</iq>

<iq type="set" to="pubsub.jabber.org" id="1">
    <query xmlns="jabber:iq:pubsub">
        <publish>
            <topic id="12345">
                <item>some kind of cdata goes here</item>
            </topic>
        </publish>
    </query>
</iq>

<iq type="set" to="pubsub.jabber.org" id="1">
    <query xmlns="jabber:iq:pubsub">
        <createtopic>
            <topic id="new_topic">
                <profile>
                    <!-- is this even remotely close?? -->
                    <publisher>pgm@jabber.org</publisher>
                    <publisher>dizzyd@jabber.org</publisher>
                </profile>
            </topic>
            <topic id="another_topic>
                <profile>
                    <publisher/>
                </profile>
            </topic>
        </createtopic>
    </query>
</iq>

<iq type="set" to="pubsub.jabber.org" id="1">
    <query xmlns="jabber:iq:pubsub">
        <removetopic>
            <topic id="12345"/>
        </removetopic>
    </query>
</iq>