mirror of
https://github.com/moparisthebest/xeps
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161 lines
7.4 KiB
XML
161 lines
7.4 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>Message Processing Hints</title>
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<abstract>This document defines a way to include hints to entities routing or receiving a message.</abstract>
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&LEGALNOTICE;
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<number>0334</number>
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<status>Deferred</status>
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<lastcall>2017-03-01</lastcall>
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<lastcall>2017-02-22</lastcall>
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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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</dependencies>
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<supersedes/>
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<supersededby/>
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<shortname>hints</shortname>
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&mwild;
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<revision>
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<version>0.3.0</version>
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<date>2018-01-25</date>
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<initials>XEP Editor (jwi)</initials>
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<remark>Defer due to lack of activity.</remark>
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</revision>
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<revision>
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<version>0.2</version>
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<date>2015-09-01</date>
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<initials>dg</initials>
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<remark>
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<p>Fixed the wrong use of no-storage instead of no-store</p>
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<p>Added a message hint <store/></p>
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</remark>
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</revision>
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<revision>
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<version>0.1</version>
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<date>2013-07-11</date>
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<initials>psa</initials>
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<remark><p>Initial published version approved by the XMPP Council.</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>2013-06-18</date>
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<initials>mw</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>Message types ('normal', 'chat', 'headline', etc.) provide an existing framework for determining how an entity should deliver or handle a message. For example &xmppim; defines that messages of type 'headline' should not be stored offline by the server, and that messages of type 'groupchat' must not be directed to other resources.</p>
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<p>However this framework of rules is quite inflexible, and new extensions are being developed that push at the boundaries of what is capable of. This specification defines a more flexible approach that allows the sender to add finer-grained 'hints' to messages, which can be used as a generic mechanism for XMPP entities to handle messages.</p>
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<p>A similar but much more extensive framework is defined in &xep0079; for applications that need it.</p>
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</section1>
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<section1 topic='Requirements' anchor='reqs'>
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<p>This specification aims to solve the following common problems, and allow a sender to hint to
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the recipient:</p>
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<ul>
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<li>Whether to store a message (e.g. for archival or as an 'offline message').</li>
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<li>Whether to copy a message to other resources.</li>
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<li>Whether to store a message that would not have been stored under normal conditions</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="Session-based stanzas" anchor='usecases-session'>
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<p>Suppose that Romeo and Juliet are avoiding the surveillance of Prince Escalus and communicating using a session-based
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encryption protocol between their laptops. In order to prevent Juliet's tablet computer that uses &xep0280; from receiving
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copies of the encrypted messages (and not being able to decrypt them), Romeo inserts the <no-copy/> hint into the
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messages he sends. Since it is also useless for these messages to be archived, he additionally adds the <no-store/>
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hint:</p>
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<example caption='Sending a message with no-copy and no-store hints'><![CDATA[
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<message
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from='romeo@montague.lit/laptop'
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to='juliet@capulet.lit/laptop'>
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<body>V unir avtug'f pybnx gb uvqr zr sebz gurve fvtug</body>
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<no-copy xmlns="urn:xmpp:hints"/>
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<no-store xmlns="urn:xmpp:hints"/>
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</message>
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]]></example>
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</section2>
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<section2 topic="Notifications" anchor='usecases-notification'>
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<p>Some automated notifications may be transient, and there would be no purpose in delaying their delivery. Such
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messages may be marked with the <no-store/> hint.</p>
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</section2>
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<section2 topic="Sensitive messages" anchor='usercases-sensitive'>
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<p>A sender may want to indicate their preference to have no permanent record of a message (also known as "off the
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record" messages), but may be happy for it to be stored temporarily as a normal part of delivery (e.g. if the
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recipient is offline at the time of sending). Such a message can be marked with the <no-permanent-store/> hint.
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</p>
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</section2>
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<section2 topic="Storage-worthy messages" anchor='store-worthy'>
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<p>Offline storage and &xep0313; can define their own rules on what messages to store and usually only store messages that contain a body element. However a sender may want to indicate that a message is worth storing even though it might not match those rules (e.g. an encrypted message that carries the payload outside the body element). Such a message can be marked with a <store/> hint.</p>
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</section2>
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</section1>
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<section1 topic="Hints" anchor="hints">
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<section2 topic="No permanent store" anchor="no-permanent-store">
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<p>The <no-permanent-store/> hint informs entities that they shouldn't store the message in
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any permanent or semi-permanent public or private archive (such as described in &xep0136; and &xep0313;)
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or in logs (such as chatroom logs).
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</p>
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</section2>
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<section2 topic="No store" anchor="no-store">
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<p>A message containing a <no-store/> hint should not be stored by a server either permanently (as above)
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or temporarily, e.g. for later delivery to an offline client, or to users not currently present in a chatroom.
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</p>
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</section2>
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<section2 topic="No copies" anchor="no-copy">
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<p>Messages with the <no-copy/> hint should not be copied to addresses other than the one to which it is
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addressed, for example through &xep0280;.</p>
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<p>This hint MUST only be included on messages addressed to full JIDs and explicitly does not override the behaviour
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defined in &xmppim; for handling messages to bare JIDs, which may involve copying to multiple resources, or multiple
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occupants in a &xep0045; room.
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</p>
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</section2>
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<section2 topic="Store">
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<p>A message containing the <store/> hint that is not of type 'error' SHOULD be stored by the entity.</p>
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</section2>
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</section1>
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<section1 topic='Business Rules' anchor='rules'>
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<p>It is important to note that message hints are, as the name implies, just hints. Implementations
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MUST NOT rely on other entities interpretation of the hints for any particular purpose.</p>
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</section1>
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<section1 topic='Security Considerations' anchor='security'>
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<p>This specification introduces no known security considerations.</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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<p>This document requires no interaction with ®ISTRAR;.</p>
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</section1>
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<section1 topic='XML 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:hints'
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xmlns='urn:xmpp:hints'
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elementFormDefault='qualified'>
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<xs:element name='no-permanent-store' type='empty'/>
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<xs:element name='no-store' type='empty'/>
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<xs:element name='no-copy' type='empty'/>
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<xs:element name='store' type='empty'/>
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<xs:simpleType name='empty'>
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<xs:restriction base='xs:string'>
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<xs:enumeration value=''/>
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</xs:restriction>
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</xs:simpleType>
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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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