xeps/xep-0452.xml

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  <!ENTITY % ents SYSTEM 'xep.ent'>
%ents;
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<xep>
<header>
  <title>MUC Mention Notifications</title>
  <abstract>This specification documents how a user may be informed when they're mentioned in a MUC which they're not currently joined to.</abstract>
  &LEGALNOTICE;
  <number>0452</number>
  <status>Experimental</status>
  <type>Standards Track</type>
  <sig>Standards</sig>
  <approver>Council</approver>
  <dependencies>
    <spec>XMPP Core</spec>
    <spec>XEP-0001</spec>
    <spec>Etc.</spec>
  </dependencies>
  <supersedes/>
  <supersededby/>
  <shortname>NOT_YET_ASSIGNED</shortname>
  &jcbrand;
  <author>
    <firstname>Severino</firstname>
    <surname>Ferrer de la Peñita</surname>
    <email>soul@blastersklan.com</email>
    <jid>soul@blastersklan.com</jid>
  </author>
  &mwild;
  <revision>
    <version>0.2.1</version>
    <date>2021-02-12</date>
    <initials>ps</initials>
    <remark>Fix reference to XEP-0297: Stanza Forwarding</remark>
  </revision>
  <revision>
    <version>0.2.0</version>
    <date>2021-02-09</date>
    <initials>jcb</initials>
    <remark>Require nickname registration for notifications to work</remark>
  </revision>
  <revision>
    <version>0.1.0</version>
    <date>2021-01-26</date>
    <initials>XEP Editor (jsc)</initials>
    <remark>Accepted by vote of Council on 2021-01-06.</remark>
  </revision>
  <revision>
    <version>0.0.1</version>
    <date>2020-12-17</date>
    <initials>jcb</initials>
    <remark><p>First draft.</p></remark>
  </revision>
</header>

<section1 topic='Introduction' anchor='intro'>
    <p>The &xep0045; specification does not provide for a mechanism whereby an user might be informed of being mentioned in a Multi-User Chat (MUC) without being present as an occupant of that MUC.</p>
    <p>This XEP aims to provide a standardized way in which this might be achieved.</p>
    <p>Concerning "being mentioned" in a MUC, we will rely on &xep0372; as the means whereby someone is explicitly mentioned in a MUC message.</p>
</section1>

<section1 topic='Requirements' anchor='reqs'>
  <p>A user's client must be able to receive forwarded groupchat messages from a MUC in which that user is mentioned, while not having an active session in that MUC (i.e. without joining it).</p>
  <p>For this to be possible, the MUC needs to know the user's JID and MUC nickname even when that user is not currently present in the MUC. &xep0045; section 7.10 ("Registering with a Room") describes a mechanism whereby a user can register a nickname with a MUC and it is recommended that this is the mechanism used to keep track of users across sessions.</p>
  <p>Whether or not mesages are forwarded will be determined by a configuration setting on the MUC.</p>
  <p>The MUC owner(s) will therefore determine whether notifications are sent out, and if activated, users may opt in or out (or have that done for them by a privileged user) by having their nicknames registered or not with the MUC.</p>
</section1>

<section1 topic='Use Cases' anchor='usecases'>

  <section2 topic='A MUC is configured to send out mention notifications'>
    <p>When an owner creates or configures a MUC, the service offers the option to send out mention notifications to non-present, but still affiliated users:</p>
    <example caption='Service Sends Configuration Form'><![CDATA[
<iq from='coven@chat.shakespeare.lit'
    id='create1'
    to='crone1@shakespeare.lit/desktop'
    type='result'>
  <query xmlns='http://jabber.org/protocol/muc#owner'>
    <x xmlns='jabber:x:data' type='form'>
      <field type='hidden' var='FORM_TYPE'>
        <value>http://jabber.org/protocol/muc#roomconfig</value>
      </field>
      ...
      <field
          label='Forward messages with mentions to non-present, affiiated users'
          type='boolean'
          var='muc#roomconfig_forwardmentions'>
        <value>0</value>
      </field>
      ...
    </x>
  </query>
</iq>
]]></example>
    <p>The owner specifies a value of "1" or "true" &BOOLEANNOTE; if the feature is desired:</p>
    <example caption='MUC Owner Submits Configuration Form'><![CDATA[
<iq from='coven@chat.shakespeare.lit'
    id='configure1'
    to='crone1@shakespeare.lit/desktop'
    type='set'>
  <query xmlns='http://jabber.org/protocol/muc#owner'>
    <x xmlns='jabber:x:data' type='submit'>
      <field type='hidden' var='FORM_TYPE'>
        <value>http://jabber.org/protocol/muc#roomconfig</value>
      </field>
      ...
      <field var='muc#roomconfig_forwardmentions'>
        <value>true</value>
      </field>
      ...
    </x>
  </query>
</iq>
]]></example>
    <p></p>
  </section2>

  <section2 topic='Notifying a non-present user of being mentioned in a MUC'>
    <p>When an affiliated user in a given MUC is referenced in a 'groupchat' message via &xep0372;, and the MUC is configured to forward mentions, then the MUC will forward the message stanza to the user.</p>
    <example caption='MUC forwards the message to the users client'><![CDATA[
<message to='hag66@shakespeare.lit' from='coven@chat.shakespeare.lit'>
  <mentions xmlns='urn:xmpp:mmn:0'>
    <forwarded xmlns='urn:xmpp:forward:0'>
      <delay xmlns='urn:xmpp:delay' stamp='2020-12-03T14:45:56Z'/>
      <message type='groupchat' id='ad22c55c-5a20-4185-8735-af2eb8d459a9'
          to='coven@chat.shakespeare.lit'
          from='coven@chat.shakespeare.lit/firstwitch'
          xml:lang='en'>
        <body>secondwitch: Thrice the brinded cat hath mew'd.</body>
        <reference xmlns='urn:xmpp:reference:0'
            type='mention'
            begin='0'
            uri='xmpp:hag66@shakespeare.lit'
            end='11'/>
        <stanza-id xmlns='urn:xmpp:sid:0'
                   id='5f3dbc5e-e1d3-4077-a492-693f3769c7ad'
                   by='coven@chat.shakespeare.lit'/>
      </message>
    </forwarded>
  </mentions>
</message>
]]></example>
    <p>Notice that in the example above, the entire original 'groupchat' message (including elements added server-side, like the &xep0359; stanza-id) is encapsulated inside a &xep0297; element.</p>
  </section2>
</section1>

<section1 topic='Security Considerations' anchor='security'>
  <p>Similarly to &xep0280;, the security model assumed by this document is that all of the resources for a single user are in the same trust boundary.</p>
  <p>Forwarded groupchat messages leak information of who is currently present in a MUC without requiring the user to join the MUC first to find out.</p>
  <ul>
    <li>Any forwarded copies received by a client MUST be from a valid MUC JID which matches the MUC JID of the encapsulated, forwarded mesages;</li>
    <li>any copies that do not meet this requirement MUST be ignored.</li>
  </ul>
</section1>
<section1 topic='IANA Considerations' anchor='iana'>
  <p>None.</p>
</section1>
<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
  <section2 topic='Protocol Namespaces' anchor='ns'>
    <p>The &REGISTRAR; includes 'urn:xmpp:mmn:0' in its registry of protocol namespaces (see &NAMESPACES;).</p>
    <ul>
      <li>urn:xmpp:mmn:0</li>
    </ul>
  </section2>
  <section2 topic='Protocol Versioning' anchor='registrar-versioning'>
    &NSVER;
  </section2>
</section1>
</xep>