xeps/xep-0009.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>Jabber-RPC</title>
  <abstract>This specification defines an XMPP protocol extension for transporting XML-RPC encoded requests and responses between two XMPP entities. The protocol supports all syntax and semantics of XML-RPC except that it uses XMPP instead of HTTP as the underlying transport.</abstract>
  &LEGALNOTICE;
  <number>0009</number>
  <status>Final</status>
  <type>Standards Track</type>
  <sig>Standards</sig>
  <dependencies>
    <spec>XMPP Core</spec>
    <spec>XML-RPC</spec>
  </dependencies>
  <supersedes/>
  <supersededby/>
  <shortname>jabber-rpc</shortname>
  <schemaloc>
    <url>http://www.xmpp.org/schemas/jabber-rpc.xsd</url>
  </schemaloc>
  <author>
    <firstname>DJ</firstname>
    <surname>Adams</surname>
    <email>dj.adams@pobox.com</email>
    <jid>dj@gnu.mine.nu</jid>
  </author>
  <revision>
    <version>2.1</version>
    <date>2006-02-09</date>
    <initials>psa</initials>
    <remark>Defined error handling, service discovery, security considerations, and XMPP Registrar considerations.</remark>
  </revision>
  <revision>
    <version>2.0</version>
    <date>2002-12-09</date>
    <initials>psa</initials>
    <remark>Per a vote of the Jabber Council, changed status to Final.</remark>
  </revision>
  <revision>
    <version>1.0</version>
    <date>2001-09-27</date>
    <initials>psa</initials>
    <remark>Changed status to Draft</remark>
  </revision>
  <revision>
    <version>0.1</version>
    <date>2001-09-14</date>
    <initials>dja</initials>
    <remark>Initial version</remark>
  </revision>
</header>
<section1 topic='Introduction'>
  <p>&xmlrpc; is a method of encoding RPC requests and responses in XML. The original specification defines HTTP (see &rfc2068;) as the only valid transport for XML-RPC payloads.</p>
  <p>Various initiatives exist already to transport XML-RPC payloads over Jabber. These initiatives were independent of each other and used slightly differing methods (e.g. carrying the payload in a <message/> element as opposed to an &IQ; stanza), resulting in potential interoperability problems.</p>
  <p>A working session during JabberCon 2001 resulted in a <link url="http://www.pipetree.com/jabber/jrpc.html">formalisation</link> of a single method. This document describes that method, which is labelled as Jabber-RPC to differentiate it from XML-RPC itself.</p>
</section1>
<section1 topic='Jabber-RPC'>
  <p>The &IQ; stanza is used to transport XML-RPC payloads. XML-RPC requests are transported using an &IQ; stanza of type "set", and XML-RPC responses are transported using an &IQ; stanza of type "result". An &IQ; stanza MUST NOT contain more than one request or response.</p>
  <p>The &IQ; stanza contains a single &QUERY; sub-element in the jabber:iq:rpc namespace. The direct child of the &QUERY; element will be either a single &lt;methodCall/&gt; element (in the case of a request) or a single &lt;methodResponse/&gt; element (in the case of a response). This child element will contain the XML-RPC payload. Note that the XML declaration that normally appears at the head of an XML-RPC request or response when transported as the payload of an HTTP POST request MUST BE omitted when it is transported via a Jabber &IQ; stanza.</p>
  <p>The encoding of the Jabber XML stream is UTF-8. It is assumed that the encoding of the XML-RPC payload is also UTF-8.</p>
  <p>Application-level errors will be indicated within the XML-RPC payload (as is the case with the traditional HTTP-based XML-RPC mechanism). Transport level errors will be indicated in the normal way for &IQ; stanzas -- namely, by an &IQ; stanza of type "error" and the addition of an &lt;error/&gt; tag as a direct child of the &IQ; stanza. There are no specific XML-RPC-related, transport-level errors.</p>
</section1>
<section1 topic='Examples'>
  <example caption='A typical request'><![CDATA[
<iq type='set' 
    from='requester@company-b.com/jrpc-client' 
    to='responder@company-a.com/jrpc-server' 
    id='rpc1'>
  <query xmlns='jabber:iq:rpc'>
    <methodCall>
      <methodName>examples.getStateName</methodName>
      <params>
        <param>
          <value><i4>6</i4></value>
        </param>
      </params>
    </methodCall>
  </query>
</iq>
  ]]></example>
  <example caption='A typical response'><![CDATA[
<iq type='result' 
    from='responder@company-a.com/jrpc-server' 
    to='requester@company-b.com/jrpc-client' 
    id='rpc1'>
  <query xmlns='jabber:iq:rpc'>
    <methodResponse>
      <params>
        <param>
          <value><string>Colorado</string></value>
        </param>
      </params>
    </methodResponse>
  </query>
</iq>
  ]]></example>
  <p>If the requesting entity does not have sufficient permissions to perform remote procedure calls, the responding entity MUST return a &forbidden; error:</p>
  <example caption='Requesting entity is forbidden to perform remote procedure calls'><![CDATA[
<iq type='error' 
    from='responder@company-a.com/jrpc-server' 
    to='requester@company-b.com/jrpc-client' 
    id='rpc1'>
  <query xmlns='jabber:iq:rpc'>
    <methodCall>
      <methodName>examples.getStateName</methodName>
      <params>
        <param>
          <value><i4>6</i4></value>
        </param>
      </params>
    </methodCall>
  </query>
  <error code='403' type='auth'>
    <forbidden xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
  </error>
</iq>
  ]]></example>
</section1>
<section1 topic='Service Discovery' anchor='disco'>
  <p>If an entity supports the Jabber-RPC protocol, it SHOULD advertise that fact in response to &xep0030; information ("diso#info") requests by returning an identity of "automation/rpc" and a feature of "jabber:iq:rpc":</p>
  <example caption='A disco#info query'><![CDATA[
<iq type='get' 
    from='requester@company-b.com/jrpc-client' 
    to='responder@company-a.com/jrpc-server' 
    id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
  ]]></example>
  <example caption='A disco#info response'><![CDATA[
<iq type='result' 
    to='requester@company-b.com/jrpc-client' 
    from='responder@company-a.com/jrpc-server' 
    id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
    <identity category='automation' type='rpc'/>
    <feature var='jabber:iq:rpc'/>
  </query>
</iq>
  ]]></example>
</section1>
<section1 topic='Security Considerations' anchor='security'>
  <p>An entity that supports Jabber-RPC SHOULD establish a "whitelist" of entities that are allowed to perform remote procedure calls and MUST return a &forbidden; error if entities with insufficient permissions attempt such calls.</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>The &REGISTRAR; includes 'jabber:iq:rpc' in its registry of protocol namespaces.</p>
  </section2>
  <section2 topic='Service Discovery Identity' anchor='registrar-disco'>
    <p>The XMPP Registrar includes a Service Discovery type of "rpc" within the "automation" category in its registry of service discovery identities.</p>
  </section2>
</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:rpc'
    xmlns='jabber:iq:rpc'
    elementFormDefault='qualified'>

  <xs:annotation>
    <xs:documentation>
      The protocol documented by this schema is defined in
      XEP-0009: http://www.xmpp.org/extensions/xep-0009.html

      There is no official XML schema for XML-RPC. The main body 
      of this schema has been borrowed from an unofficial schema 
      representation contained in the book "Processing XML With 
      Java" by Elliotte Rusty Harold, as located at:

      http://www.ibiblio.org/xml/books/xmljava/chapters/ch02s05.html
    </xs:documentation>
  </xs:annotation>

  <xs:element name='query'>
    <xs:complexType>
      <xs:choice minOccurs='0' maxOccurs='1'>
        <xs:element ref='methodCall'/>
        <xs:element ref='methodResponse'/>
      </xs:choice>
    </xs:complexType>
  </xs:element>

  <xs:element name="methodCall">
    <xs:complexType>
      <xs:all>
        <xs:element name="methodName">
          <xs:simpleType>
            <xs:restriction base="ASCIIString">
              <xs:pattern value="([A-Za-z0-9]|/|\.|:|_)*" />
            </xs:restriction>
          </xs:simpleType>
        </xs:element>
        <xs:element name="params" minOccurs="0" maxOccurs="1">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="param"  type="ParamType" 
                           minOccurs="0" maxOccurs="unbounded"/>
            </xs:sequence>
          </xs:complexType>
         </xs:element>
      </xs:all>
    </xs:complexType>  
  </xs:element>

  <xs:element name="methodResponse">
    <xs:complexType>
      <xs:choice>
        <xs:element name="params">
          <xs:complexType>
            <xs:sequence>
              <xs:element name="param" type="ParamType"/>
            </xs:sequence>
          </xs:complexType>
        </xs:element>
        <xs:element name="fault">
          <!-- What can appear inside a fault is very restricted -->
          <xs:complexType>
            <xs:sequence>
              <xs:element name="value">
                <xs:complexType>
                  <xs:sequence>
                    <xs:element name="struct"> 
                      <xs:complexType> 
                        <xs:sequence> 
                          <xs:element name="member" 
                                       type="MemberType">
                          </xs:element>
                          <xs:element name="member" 
                                       type="MemberType">
                          </xs:element>
                        </xs:sequence>
                      </xs:complexType>
                    </xs:element>
                  </xs:sequence>
                </xs:complexType>
              </xs:element>
            </xs:sequence>
          </xs:complexType>
         </xs:element>
      </xs:choice>
    </xs:complexType>  
  </xs:element>

  <xs:complexType name="ParamType">
    <xs:sequence>
      <xs:element name="value" type="ValueType"/>
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="ValueType" mixed="true">
    <xs:choice>
      <xs:element name="i4"            type="xs:int"/>
      <xs:element name="int"           type="xs:int"/>
      <xs:element name="string"        type="ASCIIString"/>
      <xs:element name="double"        type="xs:decimal"/>
      <xs:element name="Base64"        type="xs:base64Binary"/>
      <xs:element name="boolean"       type="NumericBoolean"/>
      <xs:element name="dateTime.iso8601" type="xs:dateTime"/>
      <xs:element name="array"         type="ArrayType"/>
      <xs:element name="struct"        type="StructType"/>
    </xs:choice>
  </xs:complexType>

  <xs:complexType name="StructType">
    <xs:sequence>
      <xs:element name="member" type="MemberType" 
                   maxOccurs="unbounded"/>
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="MemberType">
    <xs:sequence>
      <xs:element name="name"  type="xs:string" />
      <xs:element name="value" type="ValueType"/>
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="ArrayType">
    <xs:sequence>
      <xs:element name="data">
        <xs:complexType>
          <xs:sequence>
            <xs:element name="value"  type="ValueType" 
                         minOccurs="0" maxOccurs="unbounded"/>
          </xs:sequence>
        </xs:complexType>
      </xs:element>
    </xs:sequence>
  </xs:complexType>

  <xs:simpleType name="ASCIIString">
    <xs:restriction base="xs:string">
      <xs:pattern value="([ -~]|\n|\r|\t)*" />
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="NumericBoolean">
    <xs:restriction base="xs:boolean">
      <xs:pattern value="0|1" />
    </xs:restriction>
  </xs:simpleType>

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