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Add "Compare-And-Publish PubSub Items" ProtoXEP
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Florian Schmaus
parent
4de66367b2
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6c124cbbda
169
inbox/cap.xml
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169
inbox/cap.xml
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<?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>Atomically Compare-And-Publish PubSub Items</title>
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<abstract>This specification provides a mechanism to atomically Compare-And-Publish items to a PubSub node.</abstract>
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&LEGALNOTICE;
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<number>xxxx</number>
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<status>ProtoXEP</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>XEP-0030</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>cap</shortname>
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&flow;
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<revision>
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<version>0.0.1</version>
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<date>2017-04-20</date>
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<initials>fs</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>This specification provides a mechanism to atomically publish
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items to a PubSub node depending on the item ID of the node's latest
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item. This allows to prevent race conditions and avoids data
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loss in certain situations.</p>
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</section1>
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<section1 topic='Discoverying Support' anchor='disco'>
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<p>If an entity supports the Compared-And-Publish feature it MUST
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advertise the fact by returning a <feature/> with the 'var'
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attribute set to 'urn:xmpp:pubsub:cap:0' in response to a &xep0030;
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query for information.</p>
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</section1>
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<section1 topic='Compare-And-Publish PubSub Items' anchor='cap'>
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<p>In order to atomically compare-and-publish an item, a client
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sends an &IQ; with a 'pubsub' element qualified by the
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'urn:xmpp:pubsub:cap:0' namespace. The element MUST contain the same
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attributes and elements as the <publish/> element defined in
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&xep0060; <em>and</em> it MUST contain a previd attribute containing
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an item ID.</p>
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<p>The PubSub service MUST only publish the item if the node's
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latest item ID is equal to the ID found in the 'previd'
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attribute.</p>
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<example caption='Publisher publishes an item using Compare-And-Publish'><![CDATA[
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<iq type='set'
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from='hamlet@denmark.lit/blogbot'
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to='pubsub.shakespeare.lit'
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id='compare-and-publish1'>
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<pubsub xmlns='urn:xmpp:pubsub:cap:0'>
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<compare-and-publish
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node='princely_musings'
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previd='1'>
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<item>
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<entry xmlns='http://www.w3.org/2005/Atom'>
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<title>Soliloquy</title>
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<summary>
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To be, or not to be: that is the question:
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Whether 'tis nobler in the mind to suffer
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The slings and arrows of outrageous fortune,
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Or to take arms against a sea of troubles,
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And by opposing end them?
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</summary>
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<link rel='alternate' type='text/html'
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href='http://denmark.lit/2003/12/13/atom03'/>
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<id>tag:denmark.lit,2003:entry-32397</id>
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<published>2003-12-13T18:30:02Z</published>
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<updated>2003-12-13T18:30:02Z</updated>
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</entry>
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</item>
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</publish>
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</pubsub>
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</iq>
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]]></example>
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<section2 topic='Successfully published an item using Compare-And-Publish'>
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<p>If the 'previd' matched the latest item's ID and if the service
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was able to successfully process the request then the protocol
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continues as defined in <cite>XEP-0060 7.1.2</cite>.</p>
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</section2>
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<section2 topic='Could not publish because newest item ID did not match'>
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<p>In case the Compare-And-Publish operation failed because the
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latest node id is not the same as given in the 'previd' attribute
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in the request, the server returns an &IQ; result with 'pubsub'
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element qualified by the 'urn:xmpp:pubsub:cap:0' namespace which
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contains a <compare-and-publish-failed/> element. The
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element MUST have a 'id' attribute with the ID of the lastest
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item.</p>
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<example caption='Service returns IQ response notifying of failed Compare-And-Publish operation'><![CDATA[
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<iq type='result'
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from='pubsub.shakespeare.lit'
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to='hamlet@denmark.lit/blogbot'
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id='compare-and-ublish1'>
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<pubsub xmlns='urn:xmpp:pubsub:cap:0'>
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<compare-and-publish-failed id='2'/>
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</pubsub>
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</iq>
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]]></example>
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</section2>
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<section2 topic='Error cases'>
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<p>All other error cases are handled as specified in
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<cite>XEP-0060 § 7.1.3</cite></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>This extension protocol does not add any further security
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considerations to the ones mentioned in <cite>XEP-0060 §
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14.</cite>.</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 the Internet Assigned
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Numbers Authority (IANA).</p>
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</section1>
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<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
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<p>This specification defines the following XML namespaces:</p>
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<ul>
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<li>urn:xmpp:pubsub:cap:0</li>
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</ul>
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<code caption='Registry Submission'><![CDATA[
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<var>
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<name>urn:xmpp:pubsub:cap:0</name>
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<desc>Indicates support for Compare-And-Publish</desc>
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<doc>XEP-XXXX</doc>
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</var>]]></code>
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</section1>
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<section1 topic='XML Schema' anchor='schema'>
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<p>TODO: Add after the XEP leaves the 'experimental' state.</p>
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</section1>
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</xep>
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