mirror of
https://github.com/moparisthebest/xeps
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183 lines
8.9 KiB
XML
183 lines
8.9 KiB
XML
<?xml version='1.0' encoding='UTF-8'?>
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<!DOCTYPE xep SYSTEM 'xep.dtd' [
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<!ENTITY % ents SYSTEM 'xep.ent'>
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%ents;
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]>
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<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
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<xep>
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<header>
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<title>Component Connections</title>
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<abstract>This document specifies a standards-track XMPP protocol extension that enables server components to connect to XMPP servers.</abstract>
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&LEGALNOTICE;
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<number>0225</number>
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<status>Deferred</status>
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<type>Standards Track</type>
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<sig>Standards</sig>
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<approver>Council</approver>
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<dependencies>
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<spec>XMPP Core</spec>
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</dependencies>
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<supersedes/>
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<supersededby/>
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<shortname>component</shortname>
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&stpeter;
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<revision>
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<version>0.2</version>
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<date>2008-10-06</date>
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<initials>psa</initials>
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<remark><p>Modified namespace to incorporate namespace versioning; clarified that the value of the <hostname/> element can be either <domain> or <domain/resource>.</p></remark>
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</revision>
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<revision>
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<version>0.1</version>
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<date>2007-08-08</date>
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<initials>psa</initials>
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<remark><p>Initial published version.</p></remark>
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</revision>
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<revision>
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<version>0.0.1</version>
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<date>2007-07-31</date>
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<initials>psa</initials>
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<remark><p>First draft.</p></remark>
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</revision>
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</header>
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<section1 topic='Introduction' anchor='intro'>
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<p>&xep0114; defines a protocol that enables a server component to connect to an XMPP server. However, there are a number of perceived limitations with that protocol:</p>
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<ul>
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<li>It does not support Transport Layer Security (TLS; see &rfc5246;) for channel encryption.</li>
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<li>It does not support the Simple Authentication and Security Layer (SASL; see &rfc4422;) for authentication.</li>
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<li>It does not enable a component to bind multiple hostnames to one stream (as, for example, a client can bind multiple resource identifiers).</li>
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<li>It multiplies namespaces beyond necessity, adding the "jabber:component:accept" and "jabber:component:connect" namespaces to "jabber:client" and "jabber:server".</li>
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</ul>
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<p>This document specifies a standards-track protocol that addresses the basic requirements for component connections. In the future, additional documents may specify more advanced features on top of the protocol defined herein.</p>
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</section1>
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<section1 topic='Requirements' anchor='reqs'>
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<p>This document addresses the following requirements:</p>
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<ol>
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<li>Support Transport Layer Security for channel encryption.</li>
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<li>Support the Simple Authentication and Security Layer for authentication.</li>
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<li>Enable a component to bind multiple hostnames to one stream.</li>
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<li>Use one of the existing default namespaces for XML streams between components and servers.</li>
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</ol>
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</section1>
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<section1 topic='Stream Establishment' anchor='stream'>
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<p>XML streams are established between a component and a server exactly as they are between a client and a server as specified in &xmppcore;, with the following exceptions:</p>
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<ol>
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<li>The 'from' address of the initial stream header SHOULD be the "default" hostname of the component.</li>
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<li>The JID asserted by the end entity (in this case a component) during STARTTLS negotiation and SASL negotiation MUST be of the form <domain> in conformance with the definition of a domain identifier from XMPP Core.</li>
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<li>If a "simple user name" is included in accordance with the chosen SASL mechanism, it MUST be of the form <domain> in conformance with the definition of a domain identifier from XMPP Core.</li>
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</ol>
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</section1>
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<section1 topic='Hostname Binding' anchor='bind'>
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<p>The protocol defined in <cite>XEP-0114</cite> depended on use of the 'to' address in the stream header to specify the hostname of the component. By contrast, client-to-server connections use stream establishment is followed by binding of a resource to the stream (in fact multiple resources can be bound to the stream). This protocol emulates client-to-server connections by using a hostname binding process that is similar to the resource binding process specified in XMPP Core.</p>
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<p>If a server offers component binding over a stream, it MUST advertise a feature of "urn:xmpp:component:0".</p>
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<example caption='Stream Feature'><![CDATA[
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S: <stream:stream
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from='example.com'
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id='gPybzaOzBmaADgxKXu9UClbprp0='
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to='chat.example.com'
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version='1.0'
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xml:lang='en'
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xmlns='jabber:client'
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xmlns:stream='http://etherx.jabber.org/streams'>
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S: <stream:features>
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<bind xmlns='urn:xmpp:component:0'>
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<required/>
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</bind>
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</stream:features>
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]]></example>
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<p>In order to bind a hostname, the component sends a bind request to the server.</p>
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<example caption='Bind Request'><![CDATA[
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C: <iq id='bind_1' type='set'>
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<bind xmlns='urn:xmpp:component:0'>
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<hostname>chat.example.com</hostname>
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</bind>
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</iq>
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]]></example>
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<p>If the hostname can be bound, the server MUST return an IQ-result specifying the exact hostname that was bound.</p>
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<example caption='Bind Result'><![CDATA[
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S: <iq id='bind_1' type='result'>
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<bind xmlns='urn:xmpp:component:0'>
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<hostname>chat.example.com</hostname>
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</bind>
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</iq>
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]]></example>
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<p>If the hostname cannot be bound, the server MUST return an IQ-error, which SHOULD be &badrequest;, &conflict;, ¬allowed;, or &constraint;, just as with client resource binding as specified in <cite>RFC 3920</cite>.</p>
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<p>Note: Although the JID asserted during STARTTLS and SASL negotiation MUST be of the form <domain> (i.e., an XMPP domain identifier), the <hostname/> element MAY be of the form <domain/resource>. This form can be used for application-specific functionality (e.g., load balancing), but such functionality is out of scope for this specification.</p>
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<p>A component can send a subsequent bind request to bind another hostname (a server MUST support binding of multiple hostnames).</p>
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<example caption='Another Bind Request'><![CDATA[
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C: <iq id='bind_2' type='set'>
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<bind xmlns='urn:xmpp:component:0'>
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<hostname>foo.example.com</hostname>
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</bind>
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</iq>
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]]></example>
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<p>If the server cannot process the bind request (e.g., because the component has already bound the desired hostname), the server MUST return an IQ-error (e.g., &conflict;).</p>
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<p>A component can also unbind a resource that has already been bound (a server MUST support unbinding).</p>
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<example caption='Unbind Request'><![CDATA[
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C: <iq id='unbind_1' type='set'>
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<unbind xmlns='urn:xmpp:component:0'>
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<hostname>foo.example.com</hostname>
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</unbind>
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</iq>
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]]></example>
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<p>If the hostname can be unbound, the server MUST return an IQ-result.</p>
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<example caption='Unbind Result'><![CDATA[
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S: <iq id='unbind_1' type='result'/>
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]]></example>
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</section1>
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<section1 topic='Security Considerations' anchor='security'>
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<p>This protocol improves upon the earlier component protocol defined in <cite>XEP-0114</cite> by specifying the use of Transport Layer Security (TLS) for channel encryption and the Simple Authentication and Security Layer (SASL) for authentication. Because this protocol re-uses the XML stream establishment processes defined in XMPP Core, the security considerations from RFC 3920 and RFC 6120 apply to this protocol as well.</p>
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</section1>
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<section1 topic='IANA Considerations' anchor='iana'>
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<p>This document requires no interaction with &IANA;.</p>
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</section1>
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<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
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<section2 topic='Protocol Namespaces' anchor='registrar-ns'>
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<p>This specification defines the following XML namespace:</p>
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<ul>
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<li>urn:xmpp:component:0</li>
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</ul>
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<p>Upon advancement of this specification from a status of Experimental to a status of Draft, the ®ISTRAR; shall add the foregoing namespace to the registry located at &NAMESPACES;, as described in Section 4 of &xep0053;.</p>
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</section2>
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<section2 topic='Protocol Versioning' anchor='registrar-versioning'>
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&NSVER;
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</section2>
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</section1>
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<section1 topic='XML Schema' anchor='schema'>
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<code><![CDATA[
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<?xml version='1.0' encoding='UTF-8'?>
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<xs:schema
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xmlns:xs='http://www.w3.org/2001/XMLSchema'
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targetNamespace='urn:xmpp:component:0'
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xmlns='urn:xmpp:component:0'
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elementFormDefault='qualified'>
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<xs:element name='bind'>
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<xs:complexType>
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<xs:sequence>
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<xs:choice minOccurs='0' maxOccurs='1'>
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<xs:element name='hostname' type='xs:string'/>
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</xs:choice>
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<xs:element name='required'
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minOccurs='0'
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maxOccurs='1'
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type='empty'/>
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</xs:sequence>
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</xs:complexType>
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</xs:element>
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<xs:element name='unbind'>
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<xs:complexType>
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<xs:sequence minOccurs='0'>
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<xs:element name='hostname' type='xs:string'/>
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</xs:sequence>
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</xs:complexType>
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</xs:element>
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</xs:schema>
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]]></code>
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</section1>
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</xep>
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