mirror of
https://github.com/moparisthebest/xeps
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239 lines
9.9 KiB
XML
239 lines
9.9 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>Jingle Content Thumbnails</title>
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<abstract>This specification defines a way for a client to supply a preview image for Jingle content.</abstract>
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&LEGALNOTICE;
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<number>0264</number>
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<status>Experimental</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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&lance;
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<revision>
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<version>0.4</version>
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<date>2015-08-26</date>
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<initials>ljts</initials>
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<remark>
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<p>Changed format to use generic 'uri' attribute to allow for 'https:' and 'http:' URIs in addition to BoB 'cid:' URIs.</p>
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<p>Indicated that multiple thumbnails may be present.</p>
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<p>Expanded scope of use cases to be Jingle content in general, not just file transfer.</p>
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</remark>
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</revision>
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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>When offering a Jingle session, it can be helpful to provide a small preview of the offered content to help the session responder decide whether to accept or reject the session.</p>
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<p>This is particularly useful for file transfer content (especially image files), but can also be used for things such as video (e.g. using a still frame from the stream as the preview thumbnail), and even audio by using a small image of album cover art.</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 Jingle content description.</p>
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</section1>
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<section1 topic='Use Cases' anchor='usecase'>
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<p>When a client wishes to supply a thumbnail in a content offer, it can do so by including an extra <thumbnail/> element as shown in the following example:</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:4' senders='initiator'>
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<file>
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<media-type>image/jpeg</media>
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<name>image.jpg</name>
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<size>3032449</size>
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<hash xmlns='urn:xmpp:hashes:1' algo='sha-1'>552da749930852c69ae5d2141d3766b1</hash>
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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:1'
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uri='cid:sha1+ffd7c8d28e9c5e82afea41f97108c6b4@bob.xmpp.org'
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media-type='image/png'
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width='128'
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height='96'/>
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</file>
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</description>
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<transport .../>
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</content>
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</jingle>
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</iq>]]></example>
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<p>Thumbnails MAY be included for Jingle content other than file transfer. For example, with Jingle RTP video a thumbnail could be included to show who is calling (either by capturing a still frame from the input stream or by using an existing profile image):</p>
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<example caption='Inclusion of a thumbnail in a Jingle RTP video session'><![CDATA[
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<iq from='romeo@montague.lit/orchard'
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id='ih28sx61'
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to='juliet@capulet.lit/balcony'
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type='set'>
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<jingle xmlns='urn:xmpp:jingle:1'
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action='session-initiate'
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initiator='romeo@montague.lit/orchard'
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sid='a73sjjvkla37jfea'>
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<content creator='initiator' name='webcam'>
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<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='video'>
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<payload-type id='98' name='theora' clockrate='90000'>
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<parameter name='height' value='600'/>
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<parameter name='width' value='800'/>
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<parameter name='delivery-method' value='inline'/>
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<parameter name='configuration' value='somebase16string'/>
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<parameter name='sampling' value='YCbCr-4:2:2'/>
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</payload-type>
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<payload-type id='28' name='nv' clockrate='90000'/>
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<payload-type id='25' name='CelB' clockrate='90000'/>
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<payload-type id='32' name='MPV' clockrate='90000'/>
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<bandwidth type='AS'>128</bandwidth>
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<thumbnail xmlns='urn:xmpp:thumbs:1'
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uri='cid:sha1+ffd7c8d28e9c5e82afea41f97108c6b4@bob.xmpp.org'
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media-type='image/png'
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width='128'
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height='96'/>
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</description>
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<transport .../>
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</content>
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</jingle>
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</iq>]]></example>
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<p>Multiple <thumbnail/> elements MAY be included to provide thumbnails of different sizes, media types, or URIs.</p>
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<p>If the provided URI has the scheme 'cid', then the thumbnail data MAY be requested using &xep0231;.</p>
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</section1>
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<section1 topic='Definition of the thumbnail Element' 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>uri</td>
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<td>A URI where the thumbnail data can be accessed (typically by using a URI scheme of 'cid:', 'https:', or 'http:'). If the URI scheme is 'cid:' then the identifier MUST refer to a bit of binary data as described in &xep0231;</td>
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<td>REQUIRED</td>
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</tr>
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<tr>
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<td>media-type</td>
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<td>The value of the 'media-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. 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 the appropriate UI, such as 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 the appropriate UI, such as 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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</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, e.g. with dimensions of 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:1</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='uri' type='xs:anyURI' use='required'/>
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<xs:attribute name='media-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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