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XEP-0424: Clarify when a service must advertise disco support

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And add another disco URN for tombstones.
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JC Brand 2020-05-17 22:35:47 +02:00 committed by Jonas Schäfer
parent eb3ccc48f0
commit 457ecf3ac1
1 changed files with 36 additions and 2 deletions
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38
xep-0424.xml
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@ -26,6 +26,17 @@
<shortname>message-retract</shortname>
&lance;
&jcbrand;
<revision>
<version>0.3.0</version>
<date>2020-05-17</date>
<initials>jcb</initials>
<remark>
<ul>
<li>Clarify when a service must advertise support via disco.</li>
<li>Add another service discovery URN for tombstones.</li>
</ul>
</remark>
</revision>
<revision>
<version>0.2.1</version>
<date>2020-03-25</date>
@ -74,7 +85,8 @@
<p>Due to the federated and extensible nature of XMPP it's not possible to remove a message with full certainty and a retraction can only be considered an <strong>unenforceable request</strong> for such removal. Clients which don't support message retraction are not obligated to enforce the request and people could have seen or copied the message contents already.</p>
</section1>
<section1 topic='Discovering support' anchor='disco'>
<p>If a client or service implements message retraction, it MUST specify the 'urn:xmpp:message-retract:0' feature in its service discovery information features as specified in &xep0030; and the Entity Capabilities profile specified in &xep0115;.</p>
<p>If a client implements message retractions, it MUST specify the 'urn:xmpp:message-retract:0' feature in its service discovery information features as specified in &xep0030; and the Entity Capabilities profile specified in &xep0115;.</p>
<p>Similarly, a server that is aware of message retractions and will therefore ensure that they're archived for later retrieval (e.g.via &xep0313;), MUST also advertise the 'urn:xmpp:message-retract:0' feature.</p>
<example caption='Client requests information about a chat partner&apos;s client'><![CDATA[
<iq type='get'
from='romeo@montague.example/orchard'
@ -122,7 +134,29 @@
<section1 topic='Tombstones' anchor='tombstones'>
<p>It might be desirable to remove the retracted message from a &xep0313; service, while still recording the fact that it once existed, in order to aid clients in synchronizing their archives. To do this, the archiving service MAY replace the retracted message contents with a 'tombstone'.</p>
<p>The original message contents (i.e. the &lt;body/&gt; and any related elements which might leak information about the original message) get replaced with a &lt;retracted/&gt; element which MUST include its &lt;origin-id/&gt;, so that clients can match it to the subsequent retraction (which MUST also be stored in the archive).</p>
<p>A service which supports tombstones MUST advertise the 'urn:xmpp:message-retract:0#tombstone' feature in its Service Discovery responses.</p>
<example caption='Client requests service discovery information from the server'><![CDATA[
<iq type='get'
from='romeo@montague.example/orchard'
to='romeo@montague.example'
id='info1'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>]]></example>
<example caption='The server advertises support for tombstone retraction'><![CDATA[
<iq type='result'
to='romeo@montague.example/orchard'
from='romeo@montague.example'
id='info1'>
<query xmlns='http://jabber.org/protocol/disco#info'>
...
<feature var='urn:xmpp:message-retract:0#tombstone'/>
...
</query>
</iq>]]></example>
<p>When replacing the original message with a tombstone, the original contents (i.e. the &lt;body/&gt; and any related elements which might leak information about the original message) get replaced with a &lt;retracted/&gt; element which MUST include the &lt;origin-id/&gt;, so that clients can match it to the subsequent retraction (which MUST also be stored in the archive).</p>
<p>The &lt;retracted/&gt; element SHOULD also include a 'stamp' attribute indicating the time at which the retraction took place.</p>
<p>As with other XEP-0313 archived messages, the &xep0203; &lt;delay/&gt; element is used to indicate when the original message was received.</p>