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<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE xep SYSTEM 'xep.dtd' [
<!ENTITY % ents SYSTEM 'xep.ent'>
%ents;
]>
<?xml-stylesheet type='text/xsl' href='xep.xsl'?>
<xep>
<header>
<title>Publishing Stream Initiation Requests</title>
<abstract>This specification defines an XMPP protocol extension that enables an XMPP entity to advertise the fact that it is willing accept a particular Stream Initiation request. The protocol is used mainly to inform other entities that a particular file is available for transfer via the File Transfer protocol defined in XEP-0096.</abstract>
&LEGALNOTICE;
<number>0137</number>
<status>Draft</status>
<type>Standards Track</type>
<sig>Standards</sig>
<dependencies>
<spec>XMPP Core</spec>
<spec>XEP-0030</spec>
<spec>XEP-0095</spec>
</dependencies>
<supersedes/>
<supersededby/>
<shortname>sipub</shortname>
<schemaloc>
<url>http://www.xmpp.org/schemas/sipub.xsd</url>
</schemaloc>
&linuxwolf;
&temas;
<revision>
<version>1.0</version>
<date>2005-08-26</date>
<initials>psa</initials>
<remark>Per a vote of the Jabber Council, advanced status to Draft.</remark>
</revision>
<revision>
<version>0.3</version>
<date>2005-07-21</date>
<initials>psa</initials>
<remark>Corrected several errors in the text and examples.</remark>
</revision>
<revision>
<version>0.2</version>
<date>2004-11-03</date>
<initials>psa</initials>
<remark>Editorial review: clarified text throughout and corrected several errors in the examples.</remark>
</revision>
<revision>
<version>0.1</version>
<date>2004-06-16</date>
<initials>lw/tjm</initials>
<remark>Initial version.</remark>
</revision>
</header>
<section1 topic='Introduction' anchor='intro'>
<p>&xep0095; defines a protocol to initiate a data stream between two Jabber/XMPP entities (e.g., for the purpose of &xep0096;). However, the sender is still responsible for informing potential receivers about the existence of a given stream. This document provides an automated way for a sender to announce the availability of a stream without initiating the data transfer. The purpose is to provide a "pull" protocol that enables a receiver to then request initiation of the stream from the sender.</p>
</section1>
<section1 topic='Requirements' anchor='requirements'>
<p>This proposal addresses the following requirements:</p>
<ul>
<li>Allow a potential receiver (rather than the sender) to initiate a data stream.</li>
<li>Integrate Stream Initiation (SI) with &xep0060;.</li>
<li>Integrate Stream Initiation with &xep0004;.</li>
</ul>
</section1>
<section1 topic='Use Cases' anchor='usecase'>
<section2 topic='Publishing an SI Request' anchor='usecase.publish'>
<p>A stream owner uses the &lt;sipub/&gt; element to announce that it can perform a specific SI request. This element can be sent to a publish-subscribe (XEP-0060) node, or sent directly to potential recipients within a &MESSAGE; stanza.</p>
<p>The format of the &lt;sipub/&gt; element is as follows:</p>
<example caption='Sample &lt;sipub/&gt;'><![CDATA[
<sipub xmlns='http://jabber.org/protocol/sipub'
from='sender-jid'
id='publish-0123'
profile='si-profile'
mime-type='mime/type'>
<profile xmlns='si-profile'></profile>
</sipub>
]]></example>
<p>This format is nearly identical to that for the stream initiation &lt;si/&gt; element (see <cite>XEP-0095</cite>). The major difference is the lack of the feature negotiation for the stream methods, and the addition of a 'from' attribute.</p>
<p>The 'from' attribute SHOULD be present, and MUST be present if the stanza containing the &lt;sipub/&gt; is not from the stream owner (e.g., if the stream is advertised at a publish-subscribe node). If present, this attribute MUST be the valid JID for the stream owner.</p>
<p>The 'id' attribute is an opaque identifier. This attribute MUST be present, and MUST be a valid non-empty string. It uniquely identifies the published request at the potential sender.</p>
<p>As with stream initiation, the 'profile' attribute MUST be present, and MUST be the namespace URI governing the profile information. It identifies the format for the SI profile.</p>
<p>As with stream initiation, the 'mime-type' attribute SHOULD be present, and MUST be an IANA-registered content type. <note>The IANA registry of content types is located at &lt;<link url='http://www.iana.org/assignments/media-types/'>http://www.iana.org/assignments/media-types/</link>&gt;.</note> It provides the receiver with additional information about what the data stream will be.</p>
<p>The &lt;sipub/&gt; element MUST contain an element qualified by the namespace specified by the 'profile' attribute (e.g., &lt;file xmlns='http://jabber.org/protocol/si/profile/file-transfer'/&gt; for file transfer). This is the additional information about the data stream.</p>
<p>The &lt;sipub/&gt; information is typically provided via pubsub:</p>
<example caption='Sender advertises stream via publish-subscribe'><![CDATA[
<iq from='bard@shakespeare.lit/globe'
to='pubsub.shakespeare.lit'
id='ps1'>
<pubsub xmlns='http://jabber.org/protocol/pubsub'>
<publish node='characters'>
<sipub xmlns='http://jabber.org/protocol/sipub'
from='bard@shakespeare.lit'
id='publish-0123'
mime-type='application/pdf'
profile='http://jabber.org/protocol/si/profile/file-transfer'>
<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
name='NDA.pdf'
size='138819'
date='2004-01-28T10:07Z'>
<desc>All Shakespearean characters must sign and return this NDA ASAP</desc>
</file>
</sipub>
</publish>
</pubsub>
</iq>
]]></example>
<example caption='Pubsub service pushes announcement to all subscribers'><![CDATA[
<message from='pubsub.shakespeare.lit' to='juliet@capulet.com/balcony'>
<event xmlns='http://jabber.org/protocol/pubsub#event'>
<items node='characters'>
<item id='current'>
<sipub xmlns='http://jabber.org/protocol/sipub'
from='bard@shakespeare.lit'
id='publish-0123'
mime-type='application/pdf'
profile='http://jabber.org/protocol/si/profile/file-transfer'>
<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
name='NDA.pdf'
size='138819'
date='2004-01-28T10:07Z'>
<desc>All Shakespearean characters must sign and return this NDA ASAP</desc>
</file>
</sipub>
</item>
</items>
</event>
</message>
]]></example>
<p>The &lt;sipub/&gt; element MAY also be included directly within a &MESSAGE; stanza sent to another entity (or multiple entities, e.g., in &xep0045; or via &xep0033;). This can be especially useful for informing an offline entity about an available stream.</p>
<example caption='Advertising a stream in a message stanza'><![CDATA[
<message from='romeo@montague.net/pda' to='juliet@capulet.com'>
<sipub xmlns='http://jabber.org/protocol/sipub'
id='publish-0123'
mime-type='application/pdf'
profile='http://jabber.org/protocol/si/profile/file-transfer'>
<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
name='NDA.pdf'
size='138819'
date='2004-01-28T10:07Z'>
<desc>All Shakespearean characters must sign and return this NDA ASAP</desc>
</file>
</sipub>
</message>
]]></example>
</section2>
<section2 topic='Integration with Data Forms' anchor='usecase.xdata'>
<p>One of the goals of sipub is to integrate <cite>Stream Initiation</cite> with <cite>Data Forms</cite> to provide a "file upload" capability. This is accomplished via the datatypes specified in &xep0122;. Each datatype is specific to the profile desired.</p>
<p>For example the datatype "sipub:file-transfer" is used to identify the file upload field(s) corresponding to <cite>XEP-0096</cite>:</p>
<example caption='"Upload File" Data Forms Field'><![CDATA[
<field var='file' type='text-single' label='File to Upload'>
<validate xmlns='http://jabber.org/protocol/xdata-validate'
datatype='sipub:file-transfer'/>
</field>
]]></example>
<p>When submitting such a form, a field's value(s) MUST be the &lt;sipub/&gt; identifier(s). Also, the submitter MUST provide an &lt;sipub/&gt; element within the data form for each file to be uploaded:</p>
<example caption='Submitting an "Upload File" form'><![CDATA[
<x xmlns='jabber:x:data' type='submit'>
<field var='file'>
<value>publish-0123</value>
</field>
<sipub xmlns='http://jabber.org/protocol/sipub'
id='publish-0123'
mime-type='text/html'
profile='http://jabber.org/protocol/si/profile/file-transfer'>
<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
name='missive.html'
size='1024'
date='2005-07-21T11:21Z'/>
</sipub>
</x>
]]></example>
<p>The form processor will use this to retrieve the file(s) to be uploaded.</p>
</section2>
<section2 topic='Triggering the Stream Initiation Request' anchor='usecase.trigger'>
<p>A potential receiver starts the stream initiation session by sending an IQ-get to the sender, using the &lt;start xmlns='http://jabber.org/protocol/sipub'/&gt; element. This element contains the 'id' attribute to specify which published stream to retrieve:</p>
<example caption='Receiver requests start of stream'><![CDATA[
<iq type='get'
id='sipub-request-0'
from='juliet@capulet.com/balcony'
to='romeo@montague.net/pda'>
<start xmlns='http://jabber.org/protocol/sipub'
id='publish-0123'/>
</iq>
]]></example>
<p>If the sender accepts the request, it responds with an IQ-result containing a &lt;starting/&gt; element. This element indicates the stream initiation identifier to be used:</p>
<example caption='Sender accepts request to start stream'><![CDATA[
<iq type='result'
id='sipub-request-0'
from='romeo@montague.net/pda'
to='juliet@capulet.com/balcony'>
<starting xmlns='http://jabber.org/protocol/sipub'
sid='session-87651234'/>
</iq>
]]></example>
<p>Then the sender begins the stream initiation negotiation:</p>
<example caption='Sender starts negotiation'><![CDATA[
<iq type='set'
id='sipub-set-1'
from='romeo@montague.net/pda'
to='juliet@capulet.com/balcony'>
<si xmlns='http://jabber.org/protocol/si'
id='session-87651234'
mime-type='text/html'
profile='http://jabber.org/protocol/si/profile/file-transfer'>
<file xmlns='http://jabber.org/protocol/si/profile/file-transfer'
name='missive.html'
size='1024'
date='2005-07-21T11:21Z'>
<desc>A love letter</desc>
</file>
</si>
</iq>
]]></example>
<p>If the requested identifier is not valid, the sender SHOULD respond with a &notacceptable; error:</p>
<example caption='Sender denies because of invalid id'><![CDATA[
<iq type='error'
id='sipub-set-1'
from='romeo@montague.net/pda'
to='juliet@capulet.com/balcony'>
<start xmlns='http://jabber.org/protocol/sipub'>publish-0123</start>
<error code='405' type='modify'>
<not-acceptable xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
]]></example>
<p>If the receiver does not have permission to request the data stream, the sender SHOULD respond with a &forbidden; error:</p>
<example caption='Sender denies because receiver is forbidden'><![CDATA[
<iq type='error'
id='sipub-set-1'
from='romeo@montague.net/pda'
to='juliet@capulet.com/balcony'>
<start xmlns='http://jabber.org/protocol/sipub'>publish-0123</start>
<error code='403' type='auth'>
<forbidden xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
]]></example>
</section2>
</section1>
<section1 topic='Implementation Notes' anchor='impl-notes'>
<section2 topic='Publish ID versus SI ID'>
<p>When publishing a stream via the &lt;sipub/&gt; element, the identifier SHOULD NOT be used as-is for the &lt;si/&gt; element, since a single publication will likely result in multiple &lt;si/&gt; requests, possibly from the same receiver.</p>
</section2>
</section1>
<section1 topic='Security Considerations' anchor='security'>
<p>This document introduces no security concerns beyond those specified in <cite>XEP-0060</cite> and the relevant Stream Initiation profile in use.</p>
</section1>
<section1 topic='IANA Considerations' anchor='iana'>
<p>This document requires no interaction with &IANA;.</p>
</section1>
<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
<section2 topic='Protocol Namespaces' anchor='registrar.namespaces'>
<p>The &REGISTRAR; includes 'http://jabber.org/protocol/sipub' in its registry of protocol namespaces.</p>
</section2>
<section2 topic='Data Form Validation Datatypes' anchor='registrar.xdata-validate'>
<p>The XMPP Registrar includes 'sipub:' in its registry of Data Forms Validation Datatype Prefixes.</p>
<p>Normally, each SI profile that wishes to be considered for use with Data Forms MUST register its own datatype qualified by the "sipub:" prefix. However, this document provides an initial seed, based on the currently accepted SI profiles. The following datatypes shall be registered for use with Data Forms Validation:</p>
<code caption='Data Forms Validation Datatypes Registry Submission'><![CDATA[
<datatype>
<name>sipub:file-transfer</name>
<desc>Datatype for publishing an SI using the File Transfer Profile</desc>
<doc>XEP-0096</doc>
</datatype>
]]></code>
</section2>
</section1>
<section1 topic='XML Schema' anchor='schema'>
<code><![CDATA[
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://jabber.org/protocol/sipub'
xmlns='http://jabber.org/protocol/sipub'
elementFormDefault='qualified'>
<xs:annotation>
<xs:documentation>
The protocol documented by this schema is defined in
XEP-0137: http://www.xmpp.org/extensions/xep-0137.html
</xs:documentation>
</xs:annotation>
<xs:element name='sipub'>
<xs:annotation>
<xs:documentation>This is the root content element for advertising a stream.</xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:sequence>
<xs:any namespace='##other' minOccurs='1' maxOccurs='1'/>
</xs:sequence>
<xs:attribute name='id' type='xs:string' use='required'/>
<xs:attribute name='from' type='xs:string' use='optional'/>
<xs:attribute name='mime-type' type='xs:string' use='optional'/>
<xs:attribute name='profile' type='xs:string' use='optional'/>
</xs:complexType>
</xs:element>
<xs:element name='start'>
<xs:annotation>
<xs:documentation>This is the element for requesting retrieval of a stream.</xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:attribute name='id' type='xs:string' use='required'/>
</xs:complexType>
</xs:element>
<xs:element name='starting'>
<xs:annotation>
<xs:documentation>This is the element for specifying the stream to be retrieved.</xs:documentation>
</xs:annotation>
<xs:complexType>
<xs:attribute name='sid' type='xs:string' use='required'/>
</xs:complexType>
</xs:element>
</xs:schema>
]]></code>
</section1>
</xep>