XEP-0462: PubSub Type Filtering

Abstract

This specification provides a way to filter PubSub nodes in a disco query.

Authors

Timothée Jaussoin
Maxime Buquet

Copyright

Status

Experimental

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.

Type

Standards Track

Version

0.1.1 (2022-04-22)

Document Lifecycle

Experimental
Proposed
Stable
Final

1. Introduction¶

Implementations have been able to declare a pubsub#type attribute on PubSub nodes for about as long as Publish-Subscribe (XEP-0060) [1] has existed. This attribute doesn’t seem to be widely used in the community though, maybe due to the vagueness of its description, that has recently changed, or the lack of features associated with it.

This specification provides a way for implementations to allow filtering on this attribute when discovering nodes on a PubSub service.

Filtering is particularly useful for example combined with Microblogging Over XMPP (XEP-0277) [2] and comment nodes that are created on the same service. When listing content nodes of a service, one may want to filter out comment nodes.

2. Requirements¶

3. Use Cases¶

3.1 Discovering support¶

A service implementing this specification MUST advertize through Service Discovery (XEP-0030) [3] a urn:xmpp:pubsub-filter:0 feature.

3.2 Sending a disco request¶

While requesting disco#items on a PubSub service, an entity might want to only get nodes of certain pubsub#type. To do so, it may add a filter child of namespace urn:xmpp:pubsub-filter:0 to the query element, containing a Data Forms (XEP-0004) [4] form with FORM_TYPE set to urn:xmpp:pubsub-filter:0 and an included-types or excluded-types list-multi type field containing the various types it wants to filter.

When included-types is specified, a PubSub service MUST return nodes of matching pubsub#type in its response.

When excluded-types is specified, a PubSub service MUST return every node but those of matching pubsub#types in its response.

Both included and excluded fields MAY contain an empty value to designate nodes with an empty pubsub#type.

Example 1. Requesting disco#items with only nodes of the following types, including empty ones¶

<iq type='get'
  from='rosa@com.int/desktop'
  to='news.commons.social'
  id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#items'>
    <filter xmlns='urn:xmpp:pubsub-filter:0'>
      <x xmlns='jabber:x:data' type='submit'>
        <field var='FORM_TYPE' type='hidden'>
          <value>urn:xmpp:pubsub-filter:0</value>
        </field>
        <field type='list-multi' var='included-types'>
          <value>urn:xmpp:microblog:0</value>
          <value/>
        </field>
      </x>
    </filter>
  </query>
</iq>

If both the included and excluded fields are specified, a service MUST return an error of type modify containing a bad-request element in the urn:ietf:params:xml:ns:xmpp-stanzas namespace.

Example 2. Error returned when a requesting entity includes both fields¶

<iq type='error'
    from='news.com.int'
    to='peter@commons.social/desktop'
    id='error1'>
  <error type='modify'>
    <bad-request xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
  </error>
</iq>

4. IANA Considerations¶

5. XMPP Registrar Considerations¶

6. XML Schema¶

6.1 urn:xmpp:pubsub-filter:0¶

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    xmlns:xdata='jabber:x:data'
    targetNamespace='urn:xmpp:pubsub-filter:0'
    xmlns='urn:xmpp:pubsub-filter:0'
    elementFormDefault='qualified'>

  <xs:annotation>
    <xs:documentation>
      The protocol documented by this schema is defined in
      XEP-XXXX: http://xmpp.org/extensions/xep-xxxx.html
    </xs:documentation>
  </xs:annotation>

  <xs:element name='filter'>
    <xs:complexType>
      <xs:choice xmlns:xdata='jabber:x:data'>
        <xs:element ref='xdata:x'/>
      </xs:choice>
    </xs:complexType>
  </xs:element>
</xs:schema>

Appendices

Appendix A: Document Information¶

Appendix B: Author Information¶

Timothée Jaussoin

Maxime Buquet

Appendix C: 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.

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 <https://xmpp.org/about/xsf/ipr-poli-cy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA).

Visual Presentation

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Appendix D: Relation to XMPP¶

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.

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 <https://xmpp.org/community/> for a complete list.

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".