xep-0049.xml

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE xep SYSTEM 'xep.dtd' [
  <!ENTITY % ents SYSTEM 'xep.ent'>
%ents;
]>
<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
<xep>
<header>
  <title>Private XML Storage</title>
  <abstract>This specification provides canonical documentation of the 'jabber:iq:private' namespace currently in common usage.</abstract>
  &LEGALNOTICE;
  <number>0049</number>
  <status>Active</status>
  <type>Historical</type>
  <sig>Standards</sig>
  <dependencies>
    <spec>XMPP Core</spec>
  </dependencies>
  <supersedes/>
  <supersededby/>
  <shortname>iq-private</shortname>
  <schemaloc>
    <url>http://www.xmpp.org/schemas/iq-private.xsd</url>
  </schemaloc>
  &stpeter;
  <author>
    <firstname>Russell</firstname>
    <surname>Davis</surname>
    <email>ukscone@burninghorse.com</email>
    <jid>ukscone@burninghorse.com</jid>
  </author>
  <revision>
    <version>1.2</version>
    <date>2004-03-01</date>
    <initials>psa</initials>
    <remark>Corrected several errors in the text; specified security considerations.</remark>
  </revision>
  <revision>
    <version>1.1</version>
    <date>2004-01-06</date>
    <initials>psa</initials>
    <remark>Added XML schema; specified XMPP error handling; added security, IANA, and XMPP Registrar considerations.</remark>
  </revision>
  <revision>
    <version>1.0</version>
    <date>2003-01-09</date>
    <initials>psa</initials>
    <remark>Updated status to Active per vote of the Jabber Council.</remark>
  </revision>
  <revision>
    <version>0.4</version>
    <date>2002-11-21</date>
    <initials>psa</initials>
    <remark>Fixed error handling with regard to reserved namespaces; specified error regarding empty IQ get request.</remark>
  </revision>
  <revision>
    <version>0.3</version>
    <date>2002-11-21</date>
    <initials>psa</initials>
    <remark>Added error scenarios, removed most error codes, cleaned up the text.</remark>
  </revision>
  <revision>
    <version>0.2.1</version>
    <date>2002-10-09</date>
    <initials>rkd</initials>
    <remark>Added error code table.</remark>
  </revision>
  <revision>
    <version>0.2</version>
    <date>2002-10-08</date>
    <initials>rkd</initials>
    <remark>Corrected author email and jid. Added sentence about the
	inadvisability of use.</remark>
  </revision>
  <revision>
    <version>0.1</version>
    <date>2002-10-08</date>
    <initials>rkd</initials>
    <remark>Initial version.</remark>
  </revision>
</header>
<section1 topic='Introduction'>
  <p>The 'jabber:iq:private' namespace has previously been documented in the Jabber Programmers Guide, but not in a canonical form such as the Internet-Drafts or a XEP. This specification documents the existing usage of jabber:iq:private.</p>
</section1>
<section1 topic='jabber:iq:private Namespace'>
  <section2 topic='Description'>
    <p>A Jabber client can store any arbitrary XML on the server side by sending an &IQ; stanza of type "set" to the server with a &QUERY; child scoped by the 'jabber:iq:private' namespace. The &QUERY; element MAY contain any arbitrary XML fragment as long as the root element of that fragment is scoped by its own namespace. The data can then be retrieved by sending an &IQ; stanza of type "get" with a &QUERY; child scoped by the 'jabber:iq:private' namespace, which in turn contains a child element scoped by the namespace used for storage of that fragment. Using this method, Jabber entities can store private data on the server and retrieve it whenever necessary. The data stored might be anything, as long as it is valid XML. One typical usage for this namespace is the server-side storage of client-specific preferences; another is &xep0048;.</p>
  </section2>
  <section2 topic='Methods'>
    <table caption='Description of Acceptable Methods'>
      <tr><td>get</td><td>Sent with a blank query to retrieve the private data from the server.</td></tr>
      <tr><td>set</td><td>Sent with the private XML data contained inside of a query.</td></tr>
      <tr><td>result</td><td>Returns the private data from the server.</td></tr>
      <tr><td>error</td><td>There was an error processing the request. The exact error can be found in the child error element.</td></tr>
    </table>
  </section2>
  <section2 topic='Elements'>
    <p>The root element of this namespace is query. At least one child element with a proper namespace MUST be included; otherwise the server MUST respond with a "Not Acceptable" error (see &xep0086; for information about error conditions). A client MUST NOT query for more than one namespace in a single IQ get request. However, an IQ set or result MAY contain multiple elements qualified by the same namespace.</p>

    <example caption='Client Stores Private Data'><![CDATA[
CLIENT:
<iq type="set" id="1001">
  <query xmlns="jabber:iq:private">
    <exodus xmlns="exodus:prefs">
      <defaultnick>Hamlet</defaultnick>
    </exodus>
  </query>
</iq>

SERVER:
<iq type="result"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1001"/>
]]></example>

    <example caption='Client Retrieves Private Data'><![CDATA[
CLIENT:
<iq type="get" id="1002">
  <query xmlns="jabber:iq:private">
    <exodus xmlns="exodus:prefs"/>
  </query>
</iq>

SERVER:
<iq type="result"
    from="hamlet@shakespeare.lit/denmark"
    to="hamlet@shakespeare.lit/denmark"
    id="1002">
  <query xmlns="jabber:iq:private">
    <exodus xmlns="exodus:prefs">
      <defaultnick>Hamlet</defaultnick>
    </exodus>
  </query>
</iq>
]]></example>

    <p>If a user attempts to get or set jabber:iq:private data that belongs to another user, the server MUST return a "Forbidden" or "Service Unavailable" error to the sender (the latter condition is in common use by existing implementations, although the former is preferable).</p>
    <example caption='User Attempts to Get or Set Data for Another User'><![CDATA[
CLIENT:
<iq type="set" to="hamlet@shakespeare.lit" id="1003">
  <query xmlns="jabber:iq:private">
    <exodus xmlns="exodus:prefs">
      <defaultnick>Macbeth</defaultnick>
    </exodus>
  </query>
</iq>

SERVER:
<iq type="error"
    from="hamlet@shakespeare.lit"
    to="macbeth@shakespeare.lit"
    id="1003">
  <query xmlns="jabber:iq:private">
    <exodus xmlns="exodus:prefs">
      <defaultnick>Macbeth</defaultnick>
    </exodus>
  </query>
  <error code="403" type="cancel">
    <forbidden
        xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
  </error>
</iq>
]]></example>
    <p>If a user attempts to perform an IQ get without providing a child element, the server SHOULD return a "Bad Format" error (however, some existing implementations return a "Not Acceptable" error in such circumstances):</p>
    <example caption='User Attempts to Get Data Without Specifying Child Element/Namespace'><![CDATA[
CLIENT:
<iq type="set" id="1004">
  <query xmlns="jabber:iq:private"/>
</iq>

SERVER:
<iq type="error" id="1004">
  <query xmlns="jabber:iq:private"/>
  <error code="406" type="modify">
    <bad-format
        xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
  </error>
</iq>
]]></example>
    <p>Certain namespaces are reserved in Jabber (namespaces beginning with 'jabber:' or 'http://jabber.org/', as well as 'vcard-temp'). If a user attempts to get or set jabber:iq:private data in a reserved namespace, historically some server implementations have chosen to return an error (commonly "Not Acceptable") to the sender. Such behavior is OPTIONAL, but may be encountered by clients when interacting with some existing server implementations.</p>
    <example caption='User Attempts to Get or Set Data in a Reserved Namespace'><![CDATA[
CLIENT:
<iq type="set" id="1005">
  <query xmlns="jabber:iq:private">
    <vCard xmlns="vcard-temp">
      <FN>Hamlet</FN>
    </vCard>
  </query>
</iq>

SERVER (optional error):
<iq type="error" id="1005">
  <query xmlns="jabber:iq:private">
    <vCard xmlns="vcard-temp">
      <FN>Hamlet</FN>
    </vCard>
  </query>
  <error code="406" type="modify">
    <not-acceptable
        xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
  </error>
</iq>
]]></example>
  </section2>
</section1>
<section1 topic='Error Conditions'>
    <table caption='Error Conditions used by jabber:iq:private'>
      <tr><th>Condition</th><th>Description</th></tr>
      <tr><td>Bad Format</td><td>The IQ get does not contain a child element.</td></tr>
      <tr><td>Forbidden</td><td>The IQ get or set is sent to a JID other than that of the sender.</td></tr>
      <tr><td>Not Acceptable</td><td>The IQ get or set is qualified by a reserved namespace.</td></tr>
    </table>
</section1>
<section1 topic='Security Considerations'>
  <p>A server MUST NOT allow any entity other than an authorized resource of the user to create, update, or delete private XML stored on behalf of that user.</p>
</section1>
<section1 topic='IANA Considerations'>
  <p>This document requires no interaction with &IANA;.</p>
</section1>
<section1 topic='XMPP Registrar Considerations'>
  <p>No action on the part of the &REGISTRAR; is necessary as a result of this document, since 'jabber:iq:private' is already a registered namespace.</p>
</section1>
<section1 topic='XML Schema'>
    <code><![CDATA[
<?xml version='1.0' encoding='UTF-8'?>

<xs:schema
    xmlns:xs='http://www.w3.org/2001/XMLSchema'
    targetNamespace='jabber:iq:private'
    xmlns='jabber:iq:private'
    elementFormDefault='qualified'>

  <xs:annotation>
    <xs:documentation>
      The protocol documented by this schema is defined in
      XEP-0049: http://www.xmpp.org/extensions/xep-0049.html
    </xs:documentation>
  </xs:annotation>

  <xs:element name='query'>
    <xs:complexType>
      <xs:sequence minOccurs='0'>
        <xs:any namespace='##other'/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

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