xep-0444.xml

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<!DOCTYPE xep SYSTEM 'xep.dtd' [
        <!ENTITY % ents SYSTEM 'xep.ent'>
        %ents;
        ]>
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<xep>
<header>
  <title>Message Reactions</title>
  <abstract>This specification defines a way for adding reactions to a message.</abstract>
  &LEGALNOTICE;
  <number>0444</number>
  <status>Experimental</status>
  <type>Standards Track</type>
  <sig>Standards</sig>
  <approver>Council</approver>
  <dependencies>
    <spec>XMPP Core</spec>
    <spec>XEP-0001</spec>
    <spec>XEP-0030</spec>
    <spec>XEP-0115</spec>
    <spec>XEP-0203</spec>
    <spec>XEP-0334</spec>
    <spec>XEP-0359</spec>
  </dependencies>
  <supersedes/>
  <supersededby/>
  <shortname>reactions</shortname>
  <author>
    <firstname>Natalie</firstname>
    <surname>Wirth</surname>
    <email>xsf@larma.de</email>
  </author>
  <author>
    <firstname>Marvin</firstname>
    <surname>Wissfeld</surname>
    <email>xsf@larma.de</email>
    <jid>jabber@larma.de</jid>
  </author>
  <revision>
    <version>0.2.1</version>
    <date>2024-04-15</date>
    <initials>wb</initials>
    <remark>fix grammar and spelling</remark>
  </revision>
  <revision>
    <version>0.2.0</version>
    <date>2022-12-30</date>
    <initials>NC</initials>
    <remark>Add emoji rejection mechanism.</remark>
  </revision>
  <revision>
    <version>0.1.1</version>
    <date>2022-12-30</date>
    <initials>egp</initials>
    <remark>Add the XML Schema</remark>
  </revision>
  <revision>
    <version>0.1.0</version>
    <date>2020-10-13</date>
    <initials>XEP Editor (jsc)</initials>
    <remark>Accepted by vote of Council on 2020-10-07.</remark>
  </revision>
  <revision>
    <version>0.0.1</version>
    <date>2019-07-14</date>
    <initials>nw/mw</initials>
    <remark><p>First draft.</p></remark>
  </revision>
</header>
<section1 topic='Introduction' anchor='intro'>
  <p>
    Message reactions allow to express an opinion or feeling towards a message
    in a quick and light-weight way. Reactions are described in the form of
    emojis and can enhance communication especially when chatting with multiple
    parties. Other possible uses include voting and checking to-do list items.
  </p>
  <p>
    Reactions are typically displayed in a summarized fashion visually attached
    to the message they belong to.
  </p>
  <p>
    Related work has been done in &xep0367;. However, it can't be used for
    reactions, as it would cause difficulties with non-supporting clients, is
    not tailored to emojis and does not specify removal of reactions. To solve
    these issues, this XEP introduces a separate XML element for reactions.
  </p>
</section1>
<section1 topic='Discovering support' anchor='disco'>
  <section2 topic="Basic support" anchor="disco-base">
    <p>
      If a client implements message reactions, it MUST specify the 
      'urn:xmpp:reactions:0' feature in its service discovery information features
      as specified in &xep0030; and the Entity Capabilities profile specified in &xep0115;.
    </p>
    <example caption='Client requests information about a chat partner&apos;s client'><![CDATA[
<iq type='get'
    to='romeo@montague.lit/orchard'
    from='juliet@capulet.lit/balcony'
    id='info1'>
  <query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>]]></example>
    <example caption='Partner&apos;s client advertises support for reactions'><![CDATA[
<iq type='result'
    to='juliet@capulet.lit/balcony'
    from='romeo@montague.lit/orchard'
    id='info1'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
...
    <feature var='urn:xmpp:reactions:0'/>
...
  </query>
  </iq>]]></example>
  </section2>
  <section2 topic="Restricted reactions" anchor="disco-restricted">
    <p>
      In some cases, only a limited number and/or subset
      of emojis are allowed to react to a message.
      This is particularly useful in the context of gateways to other chat
      networks that are not as permissive about which and how many emojis
      can be used for message reactions.
      MUC components may also allow room admins to restrict the subset and/or number
      of emojis per message.
    </p>
    <p>
      To allow clients to adapt their UIs, entities that have such restrictions in place
      SHOULD advertise it with &xep0128; in a &xep0004; using the
      'urn:xmpp:reactions:0:restrictions' namespace as FORM_TYPE.
    </p>
    <example caption='Entities advertises support for restricted reactions'><![CDATA[
<iq type='result'
    to='juliet@capulet.lit/balcony'
    from='romeo@montague.lit/orchard'
    id='info1'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
  ...
    <feature var='urn:xmpp:reactions:0'/>
    <x xmlns='jabber:x:data' type='result'>
      <field var='FORM_TYPE' type='hidden'>
        <value>urn:xmpp:reactions:0:restrictions</value>
      </field>
      <field var='max_reactions_per_user'>
        <value>1</value>
      </field>
      <field var='allowlist'>
        <value>💘</value>
        <value>❤️</value>
        <value>💜</value>
      </field>
    </x> 
  ...
  </query>
</iq>]]></example>
  </section2>
</section1>
<section1 topic='Use Cases' anchor='usecases'>
  <section2 topic="Sending reactions to a message" anchor="sending-reactions">
    <p>
      When a user chooses to react to a message with a certain emoji, the
      client sends a &lt;message&gt; stanza containing a &lt;reactions&gt;
      element. The chosen emoji is included in a &lt;reaction&gt; element within
      the &lt;reactions&gt; element. The message is referred to by including its
      ID or in MUCs its stanza-id as defined in &xep0359; in the 'id' attribute
      of the &lt;reactions&gt; element.
    </p>
    <example caption="Romeo sends a message"><![CDATA[
<message to='juliet@capulet.net/balcony' id='744f6e18-a57a-11e9-a656-4889e7820c76' type='chat'>
  <body>Hello, world!</body>
</message>]]></example>
    <example caption="Juliet sends a 👋 reaction to the message"><![CDATA[
<message to='romeo@capulet.net/orchard' id='7fdd29fa-a57a-11e9-b04a-4889e7820c76' type='chat'>
  <reactions id='744f6e18-a57a-11e9-a656-4889e7820c76' xmlns='urn:xmpp:reactions:0'>
    <reaction>👋</reaction>
  </reactions>
  <store xmlns="urn:xmpp:hints"/>
</message>]]></example>
  </section2>
    <section2 topic="Updating reactions to a message" anchor="updating-reactions">
      <p>
        If the user chooses to remove reactions from or add reactions to a
        message they have already reacted to, the client sends a &lt;message&gt;
        with all &lt;reaction&gt; elements that are (still or newly) applicable
        to that message.
      </p>
      <example caption="Juliet adds a 🐢 reaction to the message"><![CDATA[
<message to='romeo@capulet.net/orchard' id='96d73204-a57a-11e9-88b8-4889e7820c76' type='chat'>
  <reactions id='744f6e18-a57a-11e9-a656-4889e7820c76' xmlns='urn:xmpp:reactions:0'>
    <reaction>👋</reaction>
    <reaction>🐢</reaction>
  </reactions>
  <store xmlns="urn:xmpp:hints"/>
</message>]]></example>
      <p>
        In order to remove all reactions from a message, an empty
        &lt;reactions&gt; element is sent.
      </p>
      <example caption="Juliet removes all reactions from the message"><![CDATA[
<message to='romeo@capulet.net/orchard' id='973c9d2e-a57a-11e9-af82-4889e7820c76' type='chat'>
  <reactions id='744f6e18-a57a-11e9-a656-4889e7820c76' xmlns='urn:xmpp:reactions:0'/>
  <store xmlns="urn:xmpp:hints"/>
</message>]]></example>
  </section2>
  <section2 topic="Rejecting a reaction" anchor="rejecting">
    <p>
      Entities implementing reaction restrictions MUST reply to invalid reactions payloads
      with a message type="error" containing a 'not-acceptable' error.
      The error payload SHOULD contain a human-readable text message explaining the reaction rules.
    </p>
    <example caption="Romeo sends a message"><![CDATA[
<message from="romeo@legacy-love-network.capulet.net"
        to='juliet@capulet.net'
        id='restricted-reactions-1'
        type='chat'>
  <body>I shall only accept heart emojis as reactions</body>
</message>]]></example>
    <example caption="Juliet reacts with both a 💘 and a 💜"><![CDATA[
<message from="juliet@capulet.net"
        to='romeo@legacy-love-network.capulet.net'
        id='will-be-rejected1'
        type='chat'>
  <reactions id='restricted-reactions-1' xmlns='urn:xmpp:reactions:0'>
    <reaction>💘</reaction>
    <reaction>💜</reaction>
  </reactions>
  <store xmlns="urn:xmpp:hints"/>
</message>]]></example>
    <example caption="Romeo rejects the reactions"><![CDATA[
<message from="romeo@legacy-love-network.capulet.net"
        to="juliet@capulet.net"
        type="error"
        id="will-be-rejected1">
  <error xmlns="jabber:client" type="modify">
    <not-acceptable xmlns="urn:ietf:params:xml:ns:xmpp-stanzas" />
    <text xmlns="urn:ietf:params:xml:ns:xmpp-stanzas">
      Only 💘, ❤️ and 💜 are allowed as reactions on this legacy IM network,
      and you can only use a single emoji at once.
    </text>
  </error>
</message>]]></example>
    <p>
      When receiving this error message, the reaction-sending entity MUST revert the "message reactions"
      to its previous state in its user interface.
    </p>
  </section2>
</section1>
<section1 topic='Business Rules' anchor='rules'>
  <p>Messages MUST NOT contain more than one &lt;reactions&gt; element</p>
  <p>
    A message containing a &lt;reactions&gt; element SHOULD be of type 'chat'
    or 'groupchat'.
  </p>
  <p>
    A &lt;reaction&gt; element SHOULD only contain Unicode codepoints that can
    be displayed as a single emoji, as specified in the latest revision of the
    <link url="http://www.unicode.org/reports/tr51/">Unicode® Technical Standard #51</link> <note>Unicode® Technical Standard #51 &lt;<link url="http://www.unicode.org/reports/tr51/">http://www.unicode.org/reports/tr51/</link>&gt;.</note>.
    Receiving entities MAY ignore &lt;reaction&gt; elements that do not comply
    with this specification.
  </p>
  <p>
    A receiving client SHOULD show reactions attached to the message they were
    in response to. Reactions MAY be displayed in a summarized fashion.
  </p>
  <p>
    A &lt;reactions&gt; element MUST NOT contain the same reaction more than
    once. A receiving entity SHOULD ignore duplicate reactions inside a
    &lt;reactions&gt; element.
  </p>
  <p>
    The sending entity SHOULD add a &lt;store/&gt; hint, as defined in &xep0334;,
    if the message being reacted to does not carry a &lt;no-store/&gt; hint.
  </p>
  <p>
    If a message is updated using &xep0308;, the 'id' attribute of the
    &lt;reactions&gt; element SHOULD reference the original message ID.
    A receiving entity SHOULD accept messages with a &lt;reactions&gt; element
    referencing a message correction and SHOULD handle such elements as if
    it was using the message ID of the original message.
  </p>
  <section2 topic='Acceptable reactions' anchor='acceptable-reactions'>
    <p>
      In direct conversations, a reaction MUST only be accepted if the sender's
      bare JID matches the bare JID of any of the two involved parties.
    </p>
    <p>
      In MUCs and MUC PMs, the recipient SHOULD ensure that the real bare JID of
      the sending occupant did not already send a reaction to that message to
      accept it as a new reaction, e.g. by keeping track of leave/join
      presences since the message was sent. This implies that in semi-anonymous
      MUCs it MAY be impossible to attach reactions to a message received from
      the history. A reaction MAY still be a valid reaction update (as per the
      next paragraph) if it was not accepted as a new reaction.
    </p>
    <p>
      A reaction MUST only be considered an update if it orignates from the same
      sender as a previous reaction message. In direct conversations, this means
      the bare JID MUST match the original bare JID. In MUCs and MUC PMs, the
      sender's full JID MAY not match the original full JID, but the recipient
      MUST ensure that the real bare JID of the sending occupant is the same as
      the real bare JID of the previous reaction message, e.g. by keeping track
      of leave/join presences.
    </p>
    <p>
      If a message containing a &lt;reactions&gt; element arrives delayed, which
      means it carries a &lt;delay/&gt; element as defined in &xep0203;, it SHOULD
      only be accepted if no newer reaction from the same sender was already
      accepted.
    </p>
  </section2>
  <section2 topic='Using the correct ID' anchor='business-id'>
    <p>
      For messages of type 'groupchat', the stanza's 'id' attribute MUST NOT be
      used for reactions. Instead, in group chat situations, the ID assigned to
      the stanza by the group chat itself must be used. This is discovered in a
      &lt;stanza-id&gt; element with a 'by' attribute that matches the bare JID
      of the group chat, as defined in &xep0359;.
    </p>
    <p>
      This implies that group chat messages without a &xep0359; stanza-id cannot
      be reacted to.
    </p>
    <p>
      For other message types, the sender should use the 'id' from a &xep0359;
      &lt;origin-id&gt; if present, or the value of the 'id' attribute on the
      &lt;message&gt; otherwise.
    </p>
  </section2>
</section1>
<section1 topic='IANA Considerations' anchor='iana'>
  <p>This document requires no interaction with &IANA;.</p>
</section1>
<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
  <section2 topic='Protocol Namespaces' anchor='ns'>
    <p>The &REGISTRAR; includes 'urn:xmpp:reactions:0' in its registry of protocol namespaces (see &NAMESPACES;).</p>
    <ul>
      <li>urn:xmpp:reactions:0</li>
    </ul>
  </section2>
</section1>
<section1 topic='XML Schema' anchor='schema'>
  <section2 topic='urn:xmpp:reactions:0' anchor='schema-reactions'>
    <code><![CDATA[
<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='urn:xmpp:reactions:0'
    xmlns='urn:xmpp:reactions:0'
    elementFormDefault='qualified'>

  <xs:element name='reactions'>
    <xs:complexType>
      <xs:sequence minOccurs='0' maxOccurs='unbounded'>
        <xs:element name='reaction' type='xs:string'/>
      </xs:sequence>
      <xs:attribute name='id' type='xs:string' use='required'/>
    </xs:complexType>
  </xs:element>

</xs:schema>]]></code>
  </section2>
</section1>
</xep>