Merge branch 'feature/xep-0045' into premerge

xep-0045.xml

@@ -45,6 +45,12 @@
   </schemaloc>
   <registry/>
   &stpeter;
+  <revision>
+    <version>1.34.0</version>
+    <date>2020-10-28</date>
+    <initials>jsc</initials>
+    <remark><p>Specify the use of a delay element in the initial subject message.</p></remark>
+  </revision>
   <revision>
     <version>1.33.0</version>
     <date>2020-04-15</date>
@@ -1841,7 +1847,7 @@
     </section3>
 
     <section3 topic='Room Subject' anchor='enter-subject'>
-      <p>After the room has optionally sent the discussion history to the new occupant, it SHALL send the current room subject. This is a &MESSAGE; stanza from the room JID (or from the occupant JID of the entity that set the subject), with a &SUBJECT; element but no &BODY; element, as shown in the following example.</p>
+      <p>After the room has optionally sent the discussion history to the new occupant, it SHALL send the current room subject. This is a &MESSAGE; stanza from the room JID (or from the occupant JID of the entity that set the subject), with a &SUBJECT; element but no &BODY; element, as shown in the following example. In addition, the subject SHOULD be stamped with &xep0203; information qualified by the 'urn:xmpp:delay' namespace to indicate the time at which the subject was last modified. If the &lt;delay/&gt; element is included, its 'from' attribute MUST be set to the JID of the room itself.</p>
       <example caption='Service Informs New Occupant of Room Subject'><![CDATA[
 <message
     from='coven@chat.shakespeare.lit/secondwitch'
@@ -1849,9 +1855,11 @@
     to='crone1@shakespeare.lit/desktop'
     type='groupchat'>
   <subject>Fire Burn and Cauldron Bubble!</subject>
+  <delay xmlns='urn:xmpp:delay' from='coven@chat.shakespeare.lit' stamp='1610-04-20T00:00:00Z'/>
 </message>
 ]]></example>
-      <p>If there is no subject set, the room MUST return an empty &SUBJECT; element.</p>
+      <p>Interoperability Note: The &lt;delay/&gt; element has been specified in version 1.34.0 of this document. Hence, consuming entities need to be able to deal with servers which do not send a &lt;delay/&gt; element. Most notably, this means that the presence of the &lt;delay/&gt; element cannot be used to distinguish a historic vs. a live subject change.</p>
+      <p>If there is no subject set, the room MUST return an empty &SUBJECT; element. The &lt;delay/&gt; SHOULD be included if the subject was actively cleared and MAY be omitted if the room never had a subject set.</p>
       <example caption='No Subject'><![CDATA[
 <message
     from='coven@chat.shakespeare.lit/secondwitch'