mirror of
https://github.com/moparisthebest/xeps
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223 lines
8.6 KiB
XML
223 lines
8.6 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>File Transfer Thumbnails</title>
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<abstract>This specification defines a way for a client supply a preview image for a file transfer.</abstract>
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&LEGALNOTICE;
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<number>0264</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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<spec>XEP-0096</spec>
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<spec>XEP-0231</spec>
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</dependencies>
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<supersedes/>
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<supersededby/>
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<shortname>thumbs</shortname>
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<author>
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<firstname>Marcus</firstname>
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<surname>Lundblad</surname>
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<email>ml@update.uu.se</email>
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<jid>mlundblad@jabber.org</jid>
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</author>
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<revision>
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<version>0.3</version>
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<date>2009-04-27</date>
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<initials>ml</initials>
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<remark><p>Fixed typo in author's name :).</p></remark>
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</revision>
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<revision>
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<version>0.2</version>
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<date>2009-04-06</date>
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<initials>ml</initials>
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<remark><p>Add paragraph in security section about protecting against malicious thumbnail dimensions in offer. Fixed a typo.</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>2009-04-02</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>0.0.3</version>
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<date>2009-03-10</date>
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<initials>ml</initials>
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<remark><p>Split use-case section into "Introduction", "Requirements", and "Use case".</p>
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</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>2009-02-25</date>
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<initials>ml</initials>
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<remark><p>Removed service disovery.
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Added missing namespace on thumnail elements.</p>
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</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>2009-02-23</date>
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<initials>ml</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='introduction'>
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<p>The current methods for file transfers include basic meta data about the
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file being offered (name, size, and date). There currently is no way to provide an image thumbnail for files such as photos.</p>
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</section1>
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<section1 topic='Requirements' anchor='requirements'>
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<p>This documents defines a way to include a thumbnail image as an additional metadata in a file transfer.</p>
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</section1>
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<section1 topic='Use Case' anchor='usecase'>
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<p>When a client wishes to supply a thumbnail in a transfer offer, it can do so by including an extra <![CDATA[<thumbnail/>]]> element as shown in the following exaples.</p>
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<example caption='Inclusion of a thumbnail in SI file transfer offer'><![CDATA[
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<iq type='set' id='offer1' to='receiver@jabber.org/resource'>
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<si xmlns='http://jabber.org/protocol/si'
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id='a0'
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mime-type='image/jpeg'
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profile='http://jabber.org/protocol/si/profile/file-transfer'>
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<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
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name='image.jpg'
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size='3032449'>
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<thumbnail xmlns='urn:xmpp:thumbs:0'
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cid='sha1+ffd7c8d28e9c5e82afea41f97108c6b4@bob.xmpp.org'
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mime-type='image/png'
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width='128'
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height='96'/>
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</file>
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<feature xmlns='http://jabber.org/protocol/feature-neg'>
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<x xmlns='jabber:x:data' type='form'>
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<field var='stream-method' type='list-single'>
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<option><value>http://jabber.org/protocol/bytestreams</value></option>
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<option><value>http://jabber.org/protocol/ibb</value></option>
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</field>
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</x>
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</feature>
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</si>
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</iq>
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]]>
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</example>
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<p>The receiver MAY now request the data using the protocol defined in &xep0231;.</p>
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<example caption='Inclusion of a thumbnail in a Jingle file transfer offer'><![CDATA[
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<iq from='romeo@montague.lit/orchard'
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id='nzu25s8'
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to='juliet@capulet.lit/balcony'
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type='set'>
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<jingle xmlns='urn:xmpp:jingle:0'
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action='session-initiate'
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initiator='romeo@montague.lit/orchard'
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sid='851ba2'>
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<content creator='initiator' name='a-file-offer'>
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<description xmlns='urn:xmpp:jingle:apps:file-transfer:1'>
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<offer>
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<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
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name='image.jpg'
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size='3032449'
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hash='552da749930852c69ae5d2141d3766b1'
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date='1969-07-21T02:56:15Z'>
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<desc>This is a test. If this were a real file...</desc>
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<thumbnail xmlns='urn:xmpp:thumbs:0'
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cid='sha1+ffd7c8d28e9c5e82afea41f97108c6b4@bob.xmpp.org'
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mime-type='image/png'
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width='128'
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height='96'/>
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</file>
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</offer>
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</description>
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...
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</content>
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</jingle>
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</iq>
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]]>
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</example>
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<section2 topic='Definition of the thumbnail Element'
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anchor='thumbnail_element'>
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<p>The following attributes are defined for the <thumbnail/> element.</p>
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<table caption='Attributes of the thumbnail Element'>
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<tr>
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<th>Attribute</th>
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<th>Description</th>
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<th>Inclusion</th>
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</tr>
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<tr>
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<td>cid</td>
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<td>A Content-ID that can be mapped to a cid: URL as specified in &rfc2111;. The 'cid' value SHOULD be of the form algo+hash@bob.xmpp.org, where the "algo" is the hashing algorithm used (e.g., "sha1" for the SHA-1 algorithm as specified in &rfc3174;) and the "hash" is the hex output of the algorithm applied to the binary data itself.</td>
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<td>REQUIRED</td>
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</tr>
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<tr>
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<td>mime-type</td>
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<td>The value of the 'mime-type' attribute MUST match the syntax specified in &rfc2045;. That is, the value MUST include a top-level media type, the "/" character, and a subtype; in addition, it MAY include one or more optional parameters (e.g., the "audio/ogg" MIME type in the example shown below includes a "codecs" parameter as specified in &rfc4281;). The "type/subtype" string SHOULD be registered in the &ianamedia;, but MAY be an unregistered or yet-to-be-registered value.</td>
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<td>RECOMMENDED</td>
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</tr>
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<tr>
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<td>width</td>
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<td>The intended display width of the thumbnail image. Used as a hint for the receiving client to prepare i.e. a dialog window.</td>
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<td>OPTIONAL</td>
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</tr>
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<tr>
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<td>height</td>
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<td>The intended display height of the thumbnail image. Used as a hint for the receiving client to prepare i.e. a dialog window.</td>
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<td>OPTIONAL</td>
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</tr>
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</table>
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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>The inclusion of an image thumbnail may leak information about a transfer
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otherwise taking place on an e2e encrypted file transfer stream. A client MAY
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wish to not include a thumbnail.</p>
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<p>A client MUST NOT rely on the values specified for the width and height of a thumbnail to allocate a bitmap data buffer for the thumbnail, to prevent possible DoS attacks. Also a client SHOULD apply implementation-specific limits on the thumbnails, if using these values to pepare a UI element for the thumbnail image, of f.ex. 128x128 pixels, values exceeding these would then be truncated and the thumbnail image scaled down when received.</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:thumbs:0</li>
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</ul>
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<p>The ®ISTRAR; includes this namespace in 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:thumbs:0'
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xmlns='urn:xmpp:thumbs:0'
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elementFormDefault='qualified'>
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<xs:annotation>
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<xs:documentation>
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The protocol documented by this schema is defined in
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xxx
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</xs:documentation>
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</xs:annotation>
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<xs:element name='thumbnail'>
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<xs:complexType>
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<xs:attribute name='cid' type='xs:string' use='required'/>
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<xs:attribute name='mime-type' type='xs:string' use='optional'/>
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<xs:attribute name='width' type='xs:integer' use='optional'/>
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<xs:attribute name='height' type='xs:integer' 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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