mirror of
https://github.com/moparisthebest/xeps
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219 lines
9.1 KiB
XML
219 lines
9.1 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>Pubsub Subscription Storage</title>
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<abstract>This document defines an XMPP protocol extension for storing subscriptions to Pubsub nodes.</abstract>
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&LEGALNOTICE;
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<number>0173</number>
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<status>Deferred</status>
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<type>Historical</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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<spec>XEP-0049</spec>
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<spec>XEP-0060</spec>
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</dependencies>
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<supersedes/>
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<supersededby/>
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<shortname>pubsubs</shortname>
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<author>
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<firstname>Magnus</firstname>
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<surname>Henoch</surname>
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<email>henoch@dtek.chalmers.se</email>
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<jid>legoscia@jabber.cd.chalmers.se</jid>
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</author>
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<revision>
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<version>0.1</version>
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<date>2006-02-09</date>
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<initials>psa</initials>
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<remark><p>Initial version; changed title to Pubsub Subscription Storage; changed namespace to storage:pubsubs for consistency with other storage XEPs.</p></remark>
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</revision>
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<revision>
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<version>0.0.4</version>
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<date>2005-12-11</date>
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<initials>mh</initials>
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<remark><p>Add resource attribute.</p></remark>
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</revision>
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<revision>
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<version>0.0.3</version>
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<date>2005-11-13</date>
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<initials>mh</initials>
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<remark><p>Add subscription attribute.</p></remark>
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</revision>
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<revision>
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<version>0.0.2</version>
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<date>2005-10-28</date>
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<initials>mh</initials>
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<remark><p>Fix typo and schema.</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>2005-10-25</date>
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<initials>mh</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>&xep0060; allows Jabber entities to subscribe to various kinds of information, but provides no way of remembering which nodes a user has subscribed to. Other protocols (e.g. &xep0080;, &xep0084;) allow information about a certain entity to be published to a Pubsub node. These protocols use &xep0030; to allow other entities to find the pubsub node used by a certain entity, but provide no way of performing the opposite mapping, from pubsub node to information source. This document attempts to fill that void, using &xep0049; for storing information about subscriptions.</p>
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</section1>
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<section1 topic='Requirements' anchor='reqs'>
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<p>This protocol enables Jabber clients to do the following:</p>
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<ul>
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<li>Remember which pubsub nodes the entity has subscribed to, and what kind of information is available at each node</li>
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<li>Update the mappings when subscriptions are added or removed</li>
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<li>Correlate incoming pubsub events to subscriptions</li>
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</ul>
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</section1>
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<section1 topic='Protocol' anchor='proto'>
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<p>The <subscriptions/> element qualified by the 'storage:pubsubs' namespace is the root element used in the jabber:iq:private transactions. It has zero or more <subscription/> child elements, each of which MUST possess the following attributes:</p>
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<ul>
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<li><em>jid</em> -- The JID of the pubsub service used</li>
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<li><em>node</em> -- The pubsub node at which the data is available</li>
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<li><em>subscription</em> -- The current subscription state, one of "none", "pending", "unconfigured" and "subscribed"</li>
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</ul>
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<p>Additionally, the <subscription/> element MAY possess these attributes:</p>
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<ul>
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<li><em>resource</em> -- The resource that is subscribed to this pubsub node. If the 'resource' attribute is absent, the bare JID is subscribed.</li>
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<li><em>user</em> -- The JID of the owner of this particular piece of data</li>
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<li><em>targetns</em> -- The namespace of the data in question</li>
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</ul>
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</section1>
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<section1 topic='Use Cases' anchor='usecases'>
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<section2 topic='Retrieving Existing Subscriptions' anchor='retrieving'>
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<p>In this example, the user already has a subscription to Juliet's geolocation, possibly established through another client.</p>
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<example caption='Client requests existing subscriptions'><![CDATA[
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<iq type='get' id='retrieve1'>
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<query xmlns='jabber:iq:private'>
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<subscriptions xmlns='storage:pubsubs'/>
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</query>
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</iq>
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]]></example>
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<example caption='Server returns existing subscriptions'><![CDATA[
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<iq type='result' id='retrieve1'>
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<query xmlns='jabber:iq:private'>
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<subscriptions xmlns='storage:pubsubs'>
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<subscription user='juliet@capulet.com'
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jid='pubsub.capulet.com'
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node='juliet/geoloc'
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targetns='http://jabber.org/protocol/geoloc'
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subscription='subscribed'/>
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</subscriptions>
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</query>
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</iq>
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]]></example>
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</section2>
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<section2 topic='Updating Subscriptions' anchor='updating'>
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<p>Due to the nature of XEP-0049, incremental updates are not possible; a client MUST send the entire <subscriptions/> node for each update. Before performing the update, the client SHOULD retrieve the stored subscriptions, and incorporate any changes.</p>
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<p>In this example, the user has just subscribed to Romeo's tune (see &xep0118;). Assuming that retrieving happened as in the previous use case, updating the subscriptions proceeds as follows:</p>
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<example caption='Client sends updated subscriptions'><![CDATA[
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<iq type='set' id='update1'>
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<query xmlns='jabber:iq:private'>
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<subscriptions xmlns='storage:pubsubs'>
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<subscription user='juliet@capulet.com'
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jid='pubsub.capulet.com'
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node='juliet/geoloc'
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targetns='http://jabber.org/protocol/geoloc'
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subscription='subscribed'/>
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<subscription user='romeo@montague.net'
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jid='pubsub.montague.net'
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node='5017cdc9f4a3d1450445c9096064e459'
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targetns='http://jabber.org/protocol/tune'
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subscription='subscribed'/>
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</subscriptions>
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</query>
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</iq>
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]]></example>
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<example caption='Server reports success'><![CDATA[
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<iq type='result' id='update1'/>
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]]></example>
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</section2>
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<section2 topic='Identifying Incoming Events' anchor='identifying'>
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<p>Having recorded the retrieved mappings, the client is now prepared to identify incoming pubsub events. Assume that the following event arrives:</p>
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<example caption='Client receives pubsub event'><![CDATA[
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<message
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from='pubsub.montague.net'
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to='mercutio@shakespeare.lit'>
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<event xmlns='http://jabber.org/protocol/pubsub#event'>
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<items node='5017cdc9f4a3d1450445c9096064e459'>
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<item id='current'>
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<tune xmlns='http://jabber.org/protocol/tune'>
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<artist>Yes</artist>
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<title>Heart of the Sunrise</title>
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<source>Yessongs</source>
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<track>3</track>
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<length>686</length>
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</tune>
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</item>
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</items>
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</event>
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</message>
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]]></example>
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<p>The client now knows that this information comes from romeo@montague.net.</p>
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</section2>
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</section1>
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<section1 topic='Security Considerations' anchor='security'>
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<p>Pubsub events offer an opportunity to spoof sender addresses e.g. through 'replyto' data (as specified by the &xep0033; protocol). This protocol attempts to close that hole. It does so by the following rules and assumptions:</p>
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<ul>
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<li>A client MUST add mappings (i.e. associations between a publisher's JID and a pubsub node) only from trustworthy sources, i.e. published disco items (see &xep0030;). This relies on disco information not being cracked or falsified.</li>
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<li>A client MUST retrieve mappings only from trustworthy sources, i.e. private XML storage. This assumes that no-one but the user is able to change such information.</li>
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</ul>
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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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<p>No namespaces or parameters need to be registered with the ®ISTRAR; as a result of this document.</p>
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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='storage:pubsubs'
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xmlns='storage:pubsubs'
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elementFormDefault='qualified'>
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<xs:element name='subscriptions'>
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<xs:complexType>
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<xs:sequence>
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<xs:element ref='subscription' minOccurs='0' maxOccurs='unbounded'/>
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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='subscription'>
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<xs:complexType>
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<xs:attribute name='jid' type='xs:string' use='required'/>
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<xs:attribute name='node' type='xs:string' use='required'/>
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<xs:attribute name='subscription' use='required'>
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<xs:simpleType>
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<xs:restriction base='xs:NCName'>
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<xs:enumeration value='none'/>
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<xs:enumeration value='pending'/>
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<xs:enumeration value='subscribed'/>
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<xs:enumeration value='unconfigured'/>
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</xs:restriction>
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</xs:simpleType>
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</xs:attribute>
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<xs:attribute name='resource' type='xs:string' use='optional'/>
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<xs:attribute name='user' type='xs:string' use='optional'/>
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<xs:attribute name='targetns' type='xs:string' use='optional'/>
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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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