XEP-0317: Hats

3.1 Including a Hat in Presence¶

MUC already includes a way for the room to signal the roles and affiliations of room occupants. Hats are signalled in a similar way. For example, the following presence notification would be sent by the room for an occupant who is a MUC room moderator but who also has a hat of "teacher's assistant" in an online classroom.

<presence
    from='physicsforpoets@courses.example.edu/Terry'
    id='DE5C66DE-EC7D-4ECB-844A-B717A67CCE3D'
    to='steve@example.edu/tablet'>
  <x xmlns='http://jabber.org/protocol/muc#user'>
    <item affiliation='owner' role='moderator'/>
  </x>
  <hats xmlns='urn:xmpp:hats:0'>
    <TeacherAssistant xmlns='http://tech.example.edu/hats' displayname='Teacher&apos; Assistant' xml:lang='en-us'/>
  </hats>
</presence>

Note: The format is open for debate. Possibilities include:

1. XML element in the hats namespace with name as a URI:

   <hat xmlns='urn:xmpp:hats:0' name='http://tech.example.edu/hats#TeacherAssistant' display='Teacher&apos;s Assistant' xml:lang='en-us'/>

   Pro: Clients that don't understand the 'http://tech.example.edu/hats#TeacherAssistant' semantics can at least display a human-readable name. Names can be registered with the XMPP Registrar. Also appropriate as a field name in Ad-Hoc Commands.

   Con: Not a very Jabberish way of structuring information.

2. XML element in the hats namespace with name scoped using Clark Notation:

   <hat xmlns='urn:xmpp:hats:0' name='{http://tech.example.edu/hats}TeacherAssistant' display='Teacher&apos;s Assistant' xml:lang='en-us'/>

   Pro: Clients that don't understand the 'http://tech.example.edu/hats#TeacherAssistant' semantics can at least display a human-readable name. Names can be registered with the XMPP Registrar. Also integrates well with Ad-Hoc Commands.

   Con: Not a very Jabberish way of structuring information.

3. XML element qualified by custom namespace:

   <TeacherAssistant xmlns='http://tech.example.edu/hats' displayname='Teacher&apos;s Assistant' xml:lang='en-us'/>

   Pro: A more Jabberish way to structure information.

   Con: Clients won't show anything if they don't understand the custom namespace.

As noted, a participant can wear many hats. The following example shows a participant who is a MUC room owner and both a "host" and a "presenter" in an online meeting system.

<presence
    from='meeting123@meetings.example.com/Harry'
    id='D568A74F-E062-407C-83E9-531E91526516'
    to='someone@example.com/foo'>
  <x xmlns='http://jabber.org/protocol/muc#user'>
    <item affiliation='owner' role='moderator'/>
  </x>
  <hats xmlns='urn:xmpp:hats:0'>
    <hat displayName='Host' name='http://schemas.example.com/hats#host' xml:lang='en-us'/>
    <hat displayName='Presenter' name='http://schemas.example.com/hats#presenter' xml:lang='en-us'/>
  </hats>
</presence>

3.2 Adding a Hat¶

Hats are added and removed using Ad-Hoc Commands (XEP-0050) [3].

The following flow shows how to add a hat.

<iq from='professor@example.edu/office'
    id='fdi3n2b6'
    to='physicsforpoets@courses.example.edu'
    type='set'
    xml:lang='en'>
  <command xmlns='http://jabber.org/protocol/commands'
           action='execute'
           node='urn:xmpp:hats:commands:don'/>
</iq>

Unless an error occurs, the service returns the appropriate form.

<iq from='physicsforpoets@courses.example.edu'
    id='fdi3n2b6'
    to='professor@example.edu/office'
    type='result'
    xml:lang='en'>
  <command xmlns='http://jabber.org/protocol/commands'
           node='urn:xmpp:hats:commands:don'
           sessionid='A971D19A-2226-4DAD-B261-8D0886B9A026'
           status='executing'>
    <x xmlns='jabber:x:data' type='form'>
      <title>Assigning a Hat</title>
      <instructions>Fill out this form to assign a hat.</instructions>
      <field type='hidden' var='FORM_TYPE'>
        <value>urn:xmpp:hats:commands</value>
      </field>
      <field label='User Address'
             type='jid-single'
             var='accountjid'>
        <required/>
      </field>
      <field label='The role'
             type='list-single'
             var='hat'>
        <option label='Teacher'><value>http://tech.example.edu/hats#Teacher</value></option>
        <option label='Teacher&apos;s Assistant'><value>http://tech.example.edu/hats#TeacherAssistant</value></option>
        <option label='Test Proctor'><value>http://tech.example.edu/hats#Proctor</value></option>
      </field>
    </x>
  </command>
</iq>

<iq from='professor@example.edu/office'
    id='9fens61z'
    to='physicsforpoets@courses.example.edu'
    type='set'
    xml:lang='en'>
  <command xmlns='http://jabber.org/protocol/commands'
           node='urn:xmpp:hats:commands:don'
           sessionid='A971D19A-2226-4DAD-B261-8D0886B9A026'>
    <x xmlns='jabber:x:data' type='submit'>
      <field type='hidden' var='FORM_TYPE'>
        <value>urn:xmpp:hats:commands</value>
      </field>
      <field var='accountjid'>
        <value>terry.anderson@example.edu</value>
      </field>
      <field var='hat'>
        <value>http://tech.example.edu/hats#TeacherAssistant</value>
      </field>
    </x>
  </command>
</iq>

<iq from='physicsforpoets@courses.example.edu'
    id='9fens61z'
    to='professor@example.edu/office'
    type='result'
    xml:lang='en'>
  <command xmlns='http://jabber.org/protocol/commands'
           node='urn:xmpp:hats:commands:don'
           sessionid='A971D19A-2226-4DAD-B261-8D0886B9A026'
           status='completed'/>
</iq>

Note: only one hat is added at a time, and the form uses a field of type "list-single" to enforce that logic.

3.3 Removing a Hat¶

The following flow shows how to remove a hat.

<iq from='professor@example.edu/office'
    id='fdi3n2b6'
    to='physicsforpoets@courses.example.edu'
    type='set'
    xml:lang='en'>
  <command xmlns='http://jabber.org/protocol/commands'
           action='execute'
           node='urn:xmpp:hats:commands:doff'>
    <x xmlns='jabber:x:data' type='submit'>
      <field type='hidden' var='FORM_TYPE'>
        <value>urn:xmpp:hats:commands</value>
      </field>
      <field var='accountjid'>
        <value>terry.anderson@example.edu</value>
      </field>
      <field var='hat'>
        <option label='Teacher&apos;s Assistant'><value>http://tech.example.edu/hats#TeacherAssistant</value></option>
      </field>
    </x>
  </command>
</iq>

<iq from='physicsforpoets@courses.example.edu'
    id='9fens61z'
    to='professor@example.edu/office'
    type='result'
    xml:lang='en'>
  <command xmlns='http://jabber.org/protocol/commands'
           node='urn:xmpp:hats:commands:doff'
           sessionid='A971D19A-2226-4DAD-B261-8D0886B9A026'
           status='completed'/>
</iq>

6.1 Protocol Namespaces¶

The XMPP Registrar shall add "urn:xmpp:hats:0" to its registry of protocol namespaces.

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1. XEP-0045: Multi-User Chat <https://xmpp.org/extensions/xep-0045.html>.

2. XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>.

3. XEP-0050: Ad-Hoc Commands <https://xmpp.org/extensions/xep-0050.html>.

4. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.