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  <!ENTITY % ents SYSTEM 'xep.ent'>
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<xep>
<header>
  <title>Attention</title>
  <abstract>This document defines an XMPP protocol extension for getting the attention of another user.</abstract>
  &LEGALNOTICE;
  <number>0224</number>
  <status>Proposed</status>
  <type>Standards Track</type>
  <sig>Standards</sig>
  <approver>Council</approver>
  <dependencies>
    <spec>XMPP Core</spec>
    <spec>XEP-0030</spec>
  </dependencies>
  <supersedes/>
  <supersededby/>
  <shortname>attention</shortname>
  <author>
    <firstname>Andreas</firstname>
    <surname>Monitzer</surname>
    <email>andy@monitzer.com</email>
    <jid>andy@monitzer.com</jid>
  </author>
  <revision>
    <version>0.2</version>
    <date>2008-10-01</date>
    <initials>psa</initials>
    <remark><p>Modified namespace to incorporate namespace versioning.</p></remark>
  </revision>
  <revision>
    <version>0.1</version>
    <date>2007-08-08</date>
    <initials>psa</initials>
    <remark><p>Initial published version.</p></remark>
  </revision>
  <revision>
    <version>0.0.1</version>
    <date>2007-07-03</date>
    <initials>am</initials>
    <remark><p>Initial version.</p></remark>
  </revision>
</header>
<section1 topic='Introduction' anchor='intro'>
  <p>Even though a client might be available (as stated in the most recent presence stanza), the user this client belongs to might not be focused on the client currently. &xep0132; defines a method for a physical test of user presence. Since this requires special hardware that can not be assumed to be available, this XEP defines a software-only implementation where no direct feedback is expected. This is known as 'nudge' or 'buzz' in some legacy IM protocols.</p>
  <p>It was discussed whether this should be part of &xep0085;. However, the semantics are inherently different, since it describes the sender's state, not a request to change the receiver's. Thus, a separate extension is desirable.</p>
</section1>
<section1 topic='Requirements' anchor='reqs'>
  <p>The specification addresses remotely getting the user's attention in a more assertive way than simple text messages.</p>
</section1>
<section1 topic='Protocol' anchor='protocol'>
  <p>In the following conversation, a user talks to somebody, but this user doesn't respond. The second inquiry includes an attention extension.</p>
  <example caption="User sends a regular message"><![CDATA[
<message from='calvin@usrobots.lit/lab' to='herbie@usrobots.lit/home' type='chat'>
  <body>All right, then, Herbie, give! We're waiting.</body>
</message>
  ]]></example>
  <p>When no reply is received, the sending user might want to grab the other's attention. This is done by sending a message that includes an &lt;attention/&gt; element qualified by the 'urn:xmpp:attention:0' namespace &VNOTE;. Note: The message may or may not include a &BODY; element.</p>
  <example caption="User tries to capture the other's attention"><![CDATA[
<message from='calvin@usrobots.lit/lab' to='herbie@usrobots.lit/home' type='headline'>
  <attention xmlns='urn:xmpp:attention:0'/>
  <body>Why don't you answer, Herbie?</body>
</message>
  ]]></example>
  <p>Finally, the receiving user notices the urgency of the message and responds.</p>
  <example caption="The user whose attention has been captured responds."><![CDATA[
<message from='herbie@usrobots.lit/home' to='calvin@usrobots.lit/lab' type='chat'>
  <body>I cannot. You know I cannot! Dr. Bogert and Dr. Lanning don't want me to.</body>
</message>
  ]]></example>
</section1>
<section1 topic='Business Rules' anchor='rules'>
  <p>The following rules apply to generating and processing of the attention extension.
    <ol>
      <li>Before sending an attention message stanza, the client SHOULD confirm support for it in the other client as described under <link url='#disco'>Determining Support</link>.</li>
      <li>The message stanza containing the attention extension MAY contain a body and/or other extensions, which is to be displayed along with executing the attention event.</li>
      <li>In message stanzas containing either &xep0203; data, attention extensions MUST be ignored, since this is an instant event which should not be replayed after a delay.</li>
      <li>Messages containing an attention extension SHOULD use the headline message type to avoid offline storage.</li>
      <li>Using the attention extension in &IQ; stanzas is not desirable, since this is part of the conversation.</li>
    </ol>
  </p>
</section1>
<section1 topic='Determining Support' anchor='disco'>
  <p>If an entity supports receiving the attention extension, it MUST advertise that fact in its responses to &xep0030; information ("disco#info") requests by returning a feature of "urn:xmpp:attention:0":</p>
  <example caption='A disco#info query'><![CDATA[
<iq type='get' 
    from='calvin@usrobots.lit/lab'
    to='herbie@usrobots.lit/home'
    id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
  ]]></example>
  <example caption='A disco#info response'><![CDATA[
<iq type='result' 
    from='herbie@usrobots.lit/home'
    to='calvin@usrobots.lit/lab'
    id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
    ...
    <feature var='urn:xmpp:attention:0'/>
    ...
  </query>
</iq>
  ]]></example>
  <p>In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in &xep0115;. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.</p>
</section1>
<section1 topic='Implementation Notes' anchor='impl'>
  <p>The implementation of the alert is up to the developer. Possible behavior is:</p>
  <ul>
    <li>Shaking the window.</li>
    <li>Playing a specific sound not used for any other event.</li>
    <li>Flashing the screen.</li>
    <li>Enabling external hardware such as flashlights.</li>
    <li>Let it be user customizable.</li>
  </ul>
  <p>However, since some users might not want this feature to disturb them, a client SHOULD allow the user to disable support. When the feature is disabled, it MUST NOT be advertised in disco#info.</p>
  <p>Rate-limiting might be desirable in some implementations.</p>
  <p>Formal feedback in response to the attention request to the requesting user is not specified, and so the request might be silently dropped.</p>
</section1>
<section1 topic='Security Considerations' anchor='security'>
  <p>It is RECOMMENDED that only message stanzas containing attention extensions from peers on the user's roster are accepted. Finer grained control might be implemented.</p>
</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='registrar-ns'>
    <p>This specification defines the following XML namespace:</p>
    <ul>
      <li>urn:xmpp:attention:0</li>
    </ul>
    <p>Upon advancement of this specification from a status of Experimental to a status of Draft, the &REGISTRAR; shall add the foregoing namespace to the registry located at &NAMESPACES;, as described in Section 4 of &xep0053;.</p>
  </section2>
  <section2 topic='Protocol Versioning' anchor='registrar-versioning'>
    <p>If the protocol defined in this specification undergoes a major revision that is not fully backward-compatible with an older version, or that contains significant new features, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of <cite>XEP-0053</cite>.</p>
  </section2>
</section1>
<section1 topic='XML Schema' anchor='schema'>
  <code><![CDATA[
<?xml version='1.0' encoding='UTF-8'?>

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

  <xs:element name='attention' type='empty'/>

  <xs:simpleType name='empty'>
    <xs:restriction base='xs:string'>
      <xs:enumeration value=''/>
    </xs:restriction>
  </xs:simpleType>

</xs:schema>
  ]]></code>
</section1>
<section1 topic='Acknowledgements' anchor='ack'>
  <p>The quotes have been taken from Isaac Asimov's short story "Liar!" as published in the book <cite>The Complete Robot</cite>.</p>
</section1>
</xep>
