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xeps/xep-0369.xml
Steve Kille bdcbd3070d Update 0.4 version to reflect subsequent changes
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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'?>
<?xml-stylesheet type="text/css" href="xmpp.css"?>
<xep>
<header>
<title>Mediated Information eXchange (MIX)</title>
<abstract>This document defines Mediated Information eXchange (MIX), an XMPP protocol extension for the exchange of information among multiple users through a mediating service. The protocol can be used to provide human group communication and communication between non-human entities using channels, although with greater flexibility and extensibility than existing groupchat technologies such as Multi-User Chat (MUC). MIX uses Publish-Subscribe to provide flexible access and publication, and uses Message Archive Management (MAM) to provide storage and archiving. </abstract>
&LEGALNOTICE;
<number>0369</number>
<status>Experimental</status>
<type>Standards Track</type>
<sig>Standards</sig>
<approver>Council</approver>
<dependencies>
<spec>XMPP Core</spec>
<spec>XMPP IM</spec>
<spec>XEP-0004</spec>
<spec>XEP-0030</spec>
<spec>XEP-0060</spec>
<spec>XEP-0128</spec>
<spec>XEP-0313</spec>
</dependencies>
<supersedes/>
<supersededby/>
<shortname>MIX</shortname>
&ksmithisode;
<!-- AUTHOR NOTE: replace withe xep.ent? -->
<author>
<firstname>Steve</firstname>
<surname>Kille</surname>
<email>Steve.Kille@isode.com</email>
<jid>Steve.Kille@isode.com</jid>
</author>
&stpeter;
<revision>
<version>0.4</version>
<date>2016-09-21</date>
<initials>sek</initials>
<remark><p>Clarification of MIX Proxy concept; Clarify node definitions; Make all nodes optional; Merge ACL node into configuration node; Add information node including avatar; Resolve 4.1 question by accepting provisional answer; Add discovery examples; setting and sharing Subject; Protocol to request channel information and participants; vCard Request; Private Messages; Set user preferences with XEP-0004; Remove references to member and occupant; Add Role Definition; Add Banned and Allowed Nodes; Update Configuration Definition;Add information on original id to message reflected back to sender Add XEP-0372 mechanism to reference channel and informal invite; Channel Invitations </p></remark>
</revision>
<revision>
<version>0.3.1</version>
<date>2016-09-07</date>
<initials>sek</initials>
<remark><p>Introduce MIX Proxy concept. Add MIX capability in client discovery.</p></remark>
</revision>
<revision>
<version>0.3</version>
<date>2016-09-05</date>
<initials>sek</initials>
<remark><p>Addressing comments from review of 0.2 and expansion/clarification of MUC/MIX dual working</p></remark>
</revision>
<revision>
<version>0.2.3</version>
<date>2016-09-01</date>
<initials>ssw, ks</initials>
<remark><p>Cleanup, use precis nickname for nicknames, and allow multiple subject languages.</p></remark>
</revision>
<revision>
<version>0.2.2</version>
<date>2016-08-26</date>
<initials>ssw</initials>
<remark><p>Phrasing and grammar.</p></remark>
</revision>
<revision>
<version>0.2.1</version>
<date>2016-08-25</date>
<initials>sek, egp</initials>
<remark><p>Includes Link Mauve (Emmanuel Gil PEYROT) editorial changes</p></remark>
</revision>
<revision>
<version>0.2</version>
<date>2016-08-16</date>
<initials>sek, ks</initials>
<remark><p>Significant update based on XMPP Summit discussions</p></remark>
</revision>
<revision>
<version>0.1.1</version>
<date>2016-03-17</date>
<initials>XEP Editor (ssw)</initials>
<remark><p>Fix XML in join example.</p></remark>
</revision>
<revision>
<version>0.1</version>
<date>2016-01-07</date>
<initials>XEP Editor (asw)</initials>
<remark><p>Initial published version approved by the XMPP Council.</p></remark>
</revision>
<revision>
<version>0.0.1</version>
<date>2015-10-12</date>
<initials>kis/psa</initials>
<remark><p>First draft.</p></remark>
</revision>
</header>
<section1 topic='Introduction' anchor='intro'>
<p>The Mediated Information eXchange (MIX) protocol is intended as a replacement for Multi-User Chat (MUC). MUC is a major application of XMPP that was developed in 2002 and standardized in &xep0045;. MIX implements the same basic MUC patterns in a more flexible and extensible way in order to address requirements that have emerged since MUC was developed. MIX supports all of the core chatroom features that are familiar from MUC, such as discussion topics and invitations. Like MUC, it also defines a strong access control model, including the ability to kick and ban users, to name administrators, and to provide controls as to which users can participate in channels.</p>
<p>Several reasons exist for replacing MUC:</p>
<ul>
<li>A number of use cases for group communication have emerged since MUC was first published.</li>
<li>Experience has shown that it is difficult to use MUC to build several kinds of communication applications (such as a multimedia conference focus) without undesirable adaptations.</li>
<li>It is impractical to address a number of the requirements listed in the next section with MUC or with extensions to MUC. </li>
<li>In the years after MUC was designed, both &xep0060; and &xep0313; have been developed and it is desirable to reuse these building blocks (e.g., MAM can be used for message history) rather than using the less robust methods defined in &xep0045;.</li>
</ul>
<p>Because it is anticipated that there will significant co-existence between MUC and MIX, this specification is designed so that:</p>
<ul>
<li>XMPP clients can implement MUC and this specification in a way that provides a coherent user experience.</li>
<li>XMPP servers can implement this specification and also provide a MUC interface in order to support clients that only implement MUC.</li>
</ul>
<p>If a server wishes to expose both MUC and MIX representations of chatrooms, it is recommended to do so by serving MUC and MIX on different domains, but a server MAY serve them on the same domain. The MIX service SHOULD include a reference to the MUC mirror, so that clients understanding both protocols can choose to show only one copy of the service.</p>
</section1>
<section1 topic='Requirements' anchor='reqs'>
<p>The following requirements have been identified, which MIX aims to address.</p>
<ol>
<li>A user's participation in a channel persists and is not modified by the user's client going online and offline.</li>
<li>Multiple devices associated with the same account can share the same nick in the channel, with well-defined rules making each client individually addressable.</li>
<li>Channels are not required to support or reflect presence for participants.</li>
<li>A reconnecting client can quickly resync with respect to messages and presence.</li>
<li>A user may (subject to configuration) receive messages from a channel as an invisible observer.</li>
<li>Configuration can be observed externally to the channel (e.g., list of participants, access control rights, etc.).</li>
<li>MIX services should provide mechanisms to prevent JIDs from being harvested.</li>
<li>MIX and Message Archive Management (MAM) should work well together.</li>
<li>A user can determine which channels they participate in.</li>
<li>Provide extensibility regarding data formats that can be sent within a channel (files, structured data, indications about media sources in multimedia conferences, etc.) as well as flexibility regarding which data formats a user wants to receive.</li>
<li>Enable federation of a channel across multiple servers, to provide a service equivalent to "federated MUC" &xep0289;.</li>
<li>To enable sharing of messages on a channel without requiring sharing of presence.</li>
<li>To enable sharing of presence without requiring message sending.</li>
<li>(Desirable) Make it easier to reduce duplicate traffic.</li>
</ol>
</section1>
<section1 topic='Concepts' anchor='concepts'>
<p>The following concepts underlie the design of MIX.</p>
<ol>
<li>MIX channels (roughly equivalent to MUC rooms) are hosted on one or more MIX domains, (examples: 'mix.example.com'; 'conference.example.com'; 'talk.example.com'), which are discoverable through &xep0030;. Each channel on a MIX service may then be discovered and queried.</li>
<li> In MIX each channel (e.g., 'channel@mix.example.com') is a pubsub service. This is based on the model from &xep0163; where every user JID (e.g., 'user@example.com') is its own pubsub service. </li>
<li>A channel's pubsub service contains a number of nodes for different event types or data formats. As described below, this document defines several standard nodes; however, future specifications or proprietary services can define their own nodes for extensibility.</li>
<li>Affiliations with the nodes are managed by the MIX service by channel level operations, so that the user does not have to separately manage affiliations with the individual PubSub nodes.
</li>
<li>&xep0313; (MAM) is used for all history access, with each node being individually addressable for MAM queries. This simplifies implementation compared to MUC (which had a specialized and rather limited history retrieval mechanism).</li>
<li>A client can achieve a 'quick resync' of a node by requesting just those changes it has not yet received, using standard MAM protocol. This solves the old MUC issue of either receiving duplicate messages when rejoining a room or potentially missing messages.</li>
<li>Because MAM is used for history, only those nodes that have a 'current value' need to store any items in them &mdash; e.g., 'urn:xmpp:mix:nodes:presence' and 'urn:xmpp:mix:nodes:subject' would store their current values (with older values being queryable through MAM), while 'urn:xmpp:mix:nodes:messages' would store no items.</li>
<li>A user's participation in a channel outlives their client sessions. A client which is offline will not share presence within the channel, but the associated user will still be listed as an participant. </li>
<li>Presence is sent to all participants using bare JID, whether or not the user has an online client. </li>
<li>Online clients MAY register presence, which is then shared with participants who have subscribed to presence.</li>
<li>MIX decouples addressing of channel participants from their nicknames, so that nickname changes do not affect addressing.</li>
<li>Each participant is addressable by a single bare JID, which is a proxy JID (not the user's real JID) to make it straightforward to hide the user's real JID from other channel participants. Full JIDs comprised of this bare JID plus a resource (also anonymized) are then constructed, allowing visibility into the number of online resources participating in a channel.</li>
<li>MIX requires client support and server support from the server providing the MIX service. Although some protocol is shared with MUC, MUC clients are not interoperable with MIX servers. This means that where a user chooses to use MIX, all of the users clients need to support MIX.</li>
</ol>
<section2 topic="MIX and PubSub" anchor="concepts-pubsub">
<p>MIX is based upon domains providing a MIX service, such as 'mix.shakespeare.example'. Note that although PubSub communication is used, a domain used for MIX is a MIX domain and not a standard &xep0060; domain. Like MUC, there is no requirement on the naming of these domains; the label 'mix' and the fact that it is a subdomain of a 'shakespeare.example' service are purely for example.</p>
<p>Every MIX channel is an addressable PubSub service (with additional MIX semantics) that will be addressed using a bare JID by other XMPP entities, for example coven@mix.shakespeare.example. While &xep0060; is used as the basis for the MIX model, MIX uses standard presence and groupchat messages to provide an interface to the MIX service that does not expose PubSub protocol for many of the more common functions.
</p>
</section2>
<section2 topic="MIX and MAM" anchor="concepts-mam">
<p> Historical data (such as the messages sent to the channel) is stored in an archive supporting Message Archive Management (MAM) so that clients can subsequently access this data with MAM. Each node can be archived separately (e.g., the presence node or the configuration node). MIX clients can retrieve archived information with MAM in order to quickly resync messages with regard to a channel, and can do so without providing presence information.</p>
</section2>
<section2 topic="MIX Proxy" anchor="concepts-mix-proxy">
<p>
A MIX channel does not send messages and presence directly to an XMPP MIX client. Instead it sends them to a MIX Proxy, which runs on the server which a MIX client accesses. MIX clients MUST make use of a MIX Proxy. Use of a MIX proxy enables flexible support of multiple clients for an XMPP user.
The primary model is that a user will join a channel over an extended period, and that the user (not a specific client used by the user) joins the channel. The primary subscription is with the client's bare JID. The MIX channel will send messages and presences to the MIX Proxy using the bare JID. The MIX Proxy will then send the messages and presence information to zero or more clients.
The MIX Proxy provides a number of functions.
</p>
<ol>
<li>Each MIX client will register with the MIX Proxy when it comes online. A key benefit of this approach is that MIX messages will only be sent to clients that support MIX. This enables use of clients that do not use MIX in conjunction with the MIX proxy.</li>
<li>MIX Service and Channel subscription and management is handled through the MIX proxy so that the MIX Proxy can track all subscription changes and share subscription information between MIX clients. To achieve this, a MIX client sends these MIX management queries to the MIX Proxy using the clients full JID and receives responses back from the MIX Proxy. The MIX Proxy will communicate these requests to a MIX channel from the MIX using the user's bare JID. Because the MIX Proxy is aware of subscription information, it can provide integrated support to a set of MIX clients.</li>
<li>Messages from a MIX client to a MIX channel will go direct to the MIX service and not through the MIX Proxy.</li>
<li>Messages from a MIX channel to a MIX client MUST be handled by a MIX Proxy.</li>
<li>The MIX Proxy will only send messages to online clients and will discard messages if no clients are online.
This means that a MIX client needs to resynchronize with the MIX service when it comes online. This synchronization will happen directly between the MIX client and MIX channel.</li>
<li>The MIX Proxy will know which channels are subscribed to, and so can send this list to a MIX client. Because channel subscriptions are long term, this information will be used instead of the bookmark approach used with MUC.</li>
<li>The MIX Proxy will manage channel registration and de-registration in the user's roster.</li>
<li>Different clients may wish to access different channels (e.g., a mobile client may only access a subset of the channels in which a user is interested). The MIX Proxy MAY handle sending messages only to the clients that wish for them, perhaps using a profile mechanism.</li>
</ol>
<p>
Messages being sent from MIX channel to MIX Proxy (which will be of type=groupchat) and presence information are sent to the bare JID. This means that the MIX Proxy will use a modification of the standard &rfc6121; rules.
</p>
<p>
The MIX standard specifies how the MIX channel interacts directly with XMPP clients and with the MIX Proxy.
</p>
<p>
The behaviour of a MIX Proxy and the protocol between MIX Proxy and MIX Client is not currently defined in this specification. It will be defined in one of three places.
It may be desirable in some situations to provide different service to different clients. For example, a mobile client may participate in a smaller set of MIX channels than a desktop client. This needs support from the server to which the client connects, so that MIX client and the connected server can negotiate which channels to send. This is not supported by the core MIX specification, but it is anticipated that this will be supported by another specification.
</p>
<ol>
<li> In an extension to &xep0376; (PAM) which follows a model close to MIX Proxy; or</li>
<li>In a new XEP specifically to defined MIX Proxy behavior; or</li>
<li>As a new section in a future version of the MIX Specification.</li>
</ol>
<p>QUESTION: Input is sought on the best place to standardize MIX Proxy.</p>
</section2>
<section2 topic="User Presence in MIX" anchor="concepts-presence">
<p>
MIX channels store presence in the presence node using the proxy JID of each online client for a user. User presence may be included for all or selected clients of a given user, based on client choice to publish presence. Where a user publishes presence for multiple clients, this information is available to all users subscribing to the channel presence.
</p>
<p>
External XMPP entities can direct stanzas to clients publishing their presence by sending them to the appropriate full proxy JID in the presence node. These stanzas MAY be routed to the client by the MIX channel. The choice to do this is dependent on MIX channel policy. For example, a disco request MAY be routed through the MIX channel to the client.
</p>
<p>
Presence updates are distributed by a channel to the bare JID of subscribers and then the subscriber's server will distribute to each of the subscriber's currently online clients.
</p>
</section2>
<section2 topic="Private Messages" anchor="concepts-pm">
<p>
Private messages MAY be sent to channel participants if allowed by channel policy. Private messages are
addressed to the user's bare proxy JID determined from the participants node, and routed by the MIX to the user's bare real JID, where standard distribution rules will apply.
</p>
<p>
Private messages MAY also be sent to specific clients identified by the full proxy JID of the client in the participants list, if allowed by channel policy.
</p>
</section2>
<section2 topic="Proxy JIDs and JID Visibility" anchor="proxy-jid">
<p>
MIX channels have two modes controlling JID visibility:
</p>
<table caption="JID Visibility Modes">
<tr><th>Mode</th><th>Description</th></tr>
<tr><td>'JID Visible'</td><td>In these channels, some or all participant JIDs are visible to all channel participants.</td></tr>
<tr><td>'JID&nbsp;Hidden'</td><td>In these channels, no participant JIDs are visible to channel participants, but they are visible to channel administrators.</td></tr>
</table>
<p>
A channel participant may specify their preferences for JID visibility, with one of the following values:
</p>
<table caption="JID Visibility Preference Options">
<tr><th>Preference</th><th>Description</th></tr>
<tr><td>'No JID Visibility Preference'</td><td>The users JID will be visible in JID Visible channels and hidden in JID Hidden channels.</td></tr>
<tr><td>'Prefer Hidden'</td><td>The user's JID will be hidden in JID Visible channels if the channel policy allows this.</td></tr>
<tr><td>'Enforce Hidden'</td><td>The user's JID will never be shown and the user will be removed from channel if channel administrator enforces visibility.</td></tr>
<tr><td>'Enforce Visible'</td><td>The users JID will always be shown and the user will be removed from channel if mode is changed to 'JID Hidden'.</td></tr>
</table>
<p>
The primary representation of a participant in a MIX channel is a proxy JID, which is an anonymized JID using the same domain as the channel and with the name of the channel encoded, using the format "&lt;channel&gt;+&lt;generated identifier&gt;@&lt;mix domain&gt;". They generated identifier MUST NOT contain the '+' characters. The Channel name MAY contain the '+' character. For example in the channel 'coven@mix.shakespeare.example', the user 'hag66@shakespeare.example' might have a proxy JID of 'coven+123456@mix.shakespeare.example'. The reason for the proxy JID is to support JID Hidden channels. Proxy JIDs are also used in JID Visible channels, for consistency and to enable switching of JID visibility. The "urn:xmpp:mix:nodes:jidmap" node maps from proxy JID to real JID. While a user is a participant in a Channel, the mapping between real JID and proxy JID MUST NOT be changed,
</p>
<p>
The full JIDs held in the presence nodes are anonymized using a similar mechanism. First the bare JID is mapped to a bare proxy JID, using the mapping held in the "urn:xmpp:mix:nodes:jidmap" node for the bare JID. Then the resource is replaced with a generated value. For example, 'hag66@shakespeare.example' in the channel coven might have a proxy JID of 'coven+123456@mix.shakespeare.example/789'. There is no client visible mapping of proxy full JIDs maintained as this is not needed. The MIX channel will need to maintain a mapping, to support directly addressing clients, such as for client to client disco#info queries. While an anonymized JID is held in the presence node, the mapping to real JID MUST NOT be changed. When an anonoymized full JID is added to the presence node, mapping to a real full JID that was previously in the presence node, the same anonymized JID as the previous time MAY be used or a different anonymized JID MAY be used.
</p>
</section2>
<section2 topic="Standard Nodes" anchor="concepts-nodes">
<p>The standard nodes are as follows (although note that not every channel will necessarily use each node):</p>
<table caption="Standard Nodes">
<tr><th>Name</th><th>Node</th><th>Description</th></tr>
<tr><td>Messages</td><td>'urn:xmpp:mix:nodes:messages'</td><td>For publishing messages. Each item of this node will contain a message sent to the channel.</td></tr>
<tr><td>Subject</td><td>'urn:xmpp:mix:nodes:subject'</td><td>For publishing the subject of the channels</td></tr>
<tr><td>Participants</td><td>'urn:xmpp:mix:nodes:participants'</td><td>For publishing the list of participants (identified by anonymized bare proxy JID), and identifying the nick. This is a list of users who would receive messages (by subscription to the messages node) and/or would receive presence (by subscription to the presence node).</td></tr>
<tr><td>JID Map</td><td>'urn:xmpp:mix:nodes:jidmap'</td><td>For publishing a list of anonymized bare JIDs from the participants node with a 1:1 mapping to the corresponding real JIDs.</td></tr>
<tr><td>Presence</td><td>'urn:xmpp:mix:nodes:presence'</td><td>For publishing information about the availability status of online participants, which may include multiple clients for a single participant.</td></tr>
<tr><td>Information</td><td>'urn:xmpp:mix:nodes:info'</td><td>For storing general channel information, such as description and avatar. </td></tr>
<tr><td>Allowed</td><td>'urn:xmpp:mix:nodes:allowed'</td><td>For storing JIDs that are allowed to be channel participants.</td></tr>
<tr><td>Banned</td><td>'urn:xmpp:mix:nodes:banned'</td><td>For storing JIDs that are not allowed to be channel participants. </td></tr>
<tr><td>Configuration</td><td>'urn:xmpp:mix:nodes:config'</td><td>For storing channel configuration. This information will generally be restricted to the channel owners.</td></tr>
</table>
<p>
All of the standard nodes are optional. A channel providing a service similar to MUC will typically use all of the standard nodes.
MIX provides mechanisms to allow users to conveniently subscribe to a chosen set of nodes and to unsubscribe to all nodes with a single operation.
</p>
<p>
The structure of each of the standard nodes is now considered in more detail in the rest of this section, after explaining roles.
</p>
<section3 topic="Roles" anchor="roles">
<p>
There are a number of MIX roles for each channel, listed in the following table. Rights will be assigned to the various roles in the channel configuration node.
</p>
<table caption="Channel Roles">
<tr><th>Role</th><th>Membership and Rights</th></tr>
<tr><td>Owners</td><td>These are owners of the list, as specified in the channel configuration node. Only owners are allowed to modify the channel configuration node.</td></tr>
<tr><td>Administrators</td><td>Administrators are defined in the channel configuration node. Administrators have update rights to the Allowed Node and Banned Node, so can control which users may participate in a channel. Administrators will usually be granted additional rights, such as the ability to kick users from a channel. </td></tr>
<tr><td>Participants</td><td>Participants are users listed by JID in the participants node.</td></tr>
<tr><td>Allowed</td><td>Allowed is the set of JIDs that are participants or may be allowed to become participants. A JID is allowed if it does not match entry in the banned node and either it matches an entry in the allowed node or the allowed node is not present. </td></tr>
<tr><td>Anyone</td><td>Any user, including users in the banned node.</td></tr>
</table>
<p>
There will always be at lease one owner and "anyone" will always have role occupants. Other roles may not have any role occupants. Rights are defined in a strictly hierarchical manner, so that for example Owners will always have rights that Administrators have.
</p>
</section3>
<section3 topic="Messages Node" anchor="messages-node">
<p>Items in this node will contain a message identified by a unique ID. A MIX implementation SHOULD NOT make messages available for retrieval from this node using pubsub. The recommended approach is that zero history is held in the messages node, and that this node is used for publication only. The recommended approach to retrieve message history is MAM. Users subscribe to this node to receive messages.</p>
<p>Private Messages are not stored in the messages node.</p>
</section3>
<section3 topic="Subject Node" anchor="subject-node">
<p>The subject node publishes the current subject of channel. Subject history is stored in MAM. A single item is stored in this node at a time which MUST contain a "text" element and MAY contain additional text elements. Where multiple text elements are provided, each MUST posses an xml:lang attribute that describes the natural language of the subject. The following example shows the format of a item in the subject node.</p>
<example caption="Subject Node">
<![CDATA[<items node='urn:xmpp:mix:nodes:subject'>
<item>
<text xml:lang="en">How to use Toads</text>
<text xml:lang="de">Wie benutzt man Kröten</text>
</item>
</items>]]></example>
<p>
When a user subscribes to the Subject Node, this will cause the channel to send Subject messages to the user through the MIX Proxy. This is done on initial user subscription and on subject change. Clients MAY directly read the channel subject from the Subject Node using PubSub.
</p>
</section3>
<section3 topic="Participants Node" anchor="participants-node">
<p>Each channel participant is represented as an item of the 'urn:xmpp:mix:nodes:participants' channel node. Each item is named by the bare proxy JID of the participant. For example 'coven+123456@mix.shakespeare.example' might name the node item associated with participant 'hag66@shakespeare.example'. The nick associated with the user is mandatory and is stored in the item. The nick for each channel participant MUST be different to the nick of other participants.
This node MAY be subscribed to for jid-visible channels that permit subscription to this node - this will allow users to see changes to the channel participants.
</p>
<p>If the Participants Node is not used, information on channel participants is not shared.</p>
<example caption="Value of Participants Node"><![CDATA[
<items node='urn:xmpp:mix:nodes:participants'>
<item id='coven+123456@mix.shakespeare.example'>
<participant xmlns='urn:xmpp:mix:0'
nick='thirdwitch'/>
</item>
</items>
]]></example>
</section3>
<section3 topic="JID Map Node" anchor="jid-map-node">
<p>The JID Map node is used to associate a proxy bare JID to its corresponding real bare JID. The JID Map node MUST have one entry for each entry in the Participants node.
Each item is identified by proxy bare JID, mapping to the real bare JID. This node is used to give administrator access to real JIDs and participant access to real JIDs in jid-visible channels.
In JID visible channels, all participants may subscribe to this node. In JID hidden channels, only administrators can subscribe. </p>
<example caption="Value of JID Map Node"><![CDATA[
<items node='urn:xmpp:mix:nodes:jidmap'>
<item id='coven+123456@mix.shakespeare.example'>
<participant xmlns='urn:xmpp:mix:0'
jid='hecate@mix.shakespeare.example'/>
</item>
</items>
]]></example>
</section3>
<section3 topic="Presence Node" anchor="presence-node">
<p>
The presence node contains the presence value for clients belonging to participants that choose to publish presence to the channel. A MIX channel MAY require that all participants publish presence. Each item in the presence node is identified by the full proxy JID, and contains the current presence value for that JID. The presence is encoded in the same way as data that would be sent in a presence stanza. The full JID is always used in this node. In MIX it is possible to have a 'presence-less channel' by not using this node. Access Control may be set to enforce that for each of the full JIDs in this list, the bare JID MUST be in the participants list.
</p>
<p>
This node may be subscribed to by users and this subscription MUST use the users bare JID. So presence of online clients is sent to the MIX Proxy for each user subscribed to this node. Presence is always sent using standard presence protocol.
</p>
<example caption="Value of Presence Node"><![CDATA[
<items node='urn:xmpp:mix:nodes:presence'>
<item id='coven+123456@mix.shakespeare.example/8765'>
<presence xmlns='jabber:client'>
<show>dnd</show>
<status>Making a Brew</status>
</presence>
</item>
</items>
]]></example>
</section3>
<section3 topic="Information Node" anchor="info-node">
<p>The Information node holds information about the channel. The information node is named by the name of the node, which must be present. Other elements of the information node are optional. Information history is stored in MAM. The name and description values MUST contain a "text" element and MAY contain additional text elements. Where multiple text elements are provided, each MUST posses an xml:lang attribute that describes the natural language of the subject. Users MAY subscribe to this node to receive information updates. The Information node has the following attributes:
</p>
<ul>
<li>'Name'. A short string providing a name for the channel</li>
<li>'Description'. A longer description of the channel.</li>
<li>'Administrator'. The person or role responsible for the channel, using vCard format following &xep0054;.</li>
<li>'Avatar'. An Avatar associated with the channel. This MAY be used in rosters that hold information on the channel and MAY be displayed by clients using the channel. The avatar is stored using the format defined in &xep0084;</li>
</ul>
<p>The format of the Information node follows &xep0004;. This allows configuration to be updated by MIX defined commands and that the results of update commands can be directly written to the PubSub node.
The following example shows the format of a item in the information node for the example coven@mix.shakespeare.example channel.
</p>
<example caption="Information Node"><![CDATA[
<items node='urn:xmpp:mix:nodes:info'>
<item id='2016-05-30T09:00:00' xmlns='urn:xmpp:mix:0'>
<name>Witches Coven</name>
<description>A location not far from the blasted heath where the three witches meet</description>
<administrator>
<vCard xmlns='vcard-temp'>
<FN>Hecate</FN>
<TITLE>Chief Witch</TITLE>
</vCard>
</administrator>
<avatar>
<data xmlns='urn:xmpp:avatar:data'>
qANQR1DBwU4DX7jmYZnncm...
</data>
</avatar>
</item>
</items>
]]></example>
</section3>
<section3 topic="Allowed" anchor="allowed-node">
<p>
This node represents a list of JIDs that are allowed to become participants. If the allowed node is not present, all JIDs are allowed. The allowed list is always considered in conjunction with the banned list, stored in the banned node. Only Administrators and Owners have write permission to the allowed node and are also the only roles that are allows to subscribe to this node. Each item contains a real bare JID. The following example shows how the allowed list can specify single JIDs and domains.
</p>
<example caption="Allowed Node"><![CDATA[
<items node='urn:xmpp:mix:nodes:allowed'>
<item id='@shakespeare.lit'>
<item id='alice@wonderland.lit'>
</item>
</items>
]]></example>
</section3>
<section3 topic="Banned" anchor="banned-node">
<p>
This node represents a list of JIDs that are explicitly not allowed to become participants. The values in this list take priority over values in the allowed node. Only Administrators and Owners have write permission to the allowed node and are also the only roles that are allows to subscribe to this node. Each item contains a real bare JID.
</p>
<example caption="Banned Node"><![CDATA[
<items node='urn:xmpp:mix:nodes:banned'>
<item id='lear@shakespeare.lit'>
<item id='macbeth@shakespeare.lit'>
</item>
</items>
]]></example>
</section3>
<section3 topic="Configuration Node" anchor="config-node">
<p>
The Configuration node holds the configuration of the channel as a single item, named by the date-time of the last update to the configuration. A single item is stored in the node at a time, with previous configuration history accessed by MAM. Users MAY subscribe to the configuration node to get notification of configuration change. The configuration node is optional for a MIX channel. For example, configuration choices could be fixed and not exposed. A subset of the defined configuration options may be used and additional non-standard configuration options may be added. If configuration options to control functionality of the nature described here are provided, the options defined in this standard MUST be used. The following configuration options are provided:
</p>
<ul>
<li>'Date of Configuration Change'. Encoded as the item ID.</li>
<li>'Last Change Made By'. Bare JID of the user making the last change.</li>
<li>'Owners'. List of bare JIDs with Owner rights as defined in ACL node. When a list is created, the JID creating the list is configured as an owner, unless this attribute is explicitly configured to another value. Owners will generally have full rights to make changes to channel configuration and access control.</li>
<li>'Administrators'. List of bare JIDs with Administrator rights. An Administrator has rights to make changes to channel access control and configuration as defined in ACL node. An Administrator also has operational right on a channel, such a kicking users out of the channel. These rights are analogous to moderator rights defined in &xep0045;.</li>
<li>'End of Life'. The date and time at which the channel will be automatically removed by the server. If this is not set, the channel is permanent.</li>
<li>'Nodes Present'. Specifies which nodes are present: "participants"; "presence"; "subject"; "information"; "allowed"; "banned". Note that "config" is implicit, and "jidmap" is implied by "participants". </li>
<li>'Message Node Subscription'. Controls who can subscribe to messages node: "participants"; "allowed"; "anyone". Default "participants".</li>
<li>'Participants Node Subscription'. Controls who can subscribe to participants node: "participants"; "allowed"; "anyone"; "nobody". Default "participants".</li>
<li>'Presence Node Subscription'. Controls who can subscribe to presence node: "participants"; "allowed"; "anyone"; "nobody". Default "participants".</li>
<li>'Subject Node Subscription'. Controls who can subscribe to subject node: "participants"; "allowed"; "anyone"; "nobody". Default "participants".</li>
<li>'Configuration Node Access'. Controls who can subscribe to and has read access configuration node: "participants"; "admins"; "owners"; "nobody". Default "admins".</li>
<li>'Kick Rights'. Controls who can kick users from the channel: "admins"; "owners"; "nobody". Default "admins".</li>
<li>'JID Visibility'. Choice of "jid-hidden", "jid-optionally-visible", "jid-mandatory-visible". </li>
<li>'Open Presence'. If selected, any client may register presence. If not selected, only clients with bare JID in the participants list may register presence.</li>
<li>'Allow Message Retraction'. If this option is selected users will be able to retract messages sent to the MIX channel.</li>
<li>'Participation Addition by Invitation from Participant'. This option extends a channel so that a channel participant has rights to invite and enable other users as participants.
</li>
<li>'No Private Messages'. If this option is selected, private messages may not be used with the channel.</li>
</ul>
<p>AUTHOR'S NOTE: This version contains a number of AUTHOR NOTES, which are reminder instructions to the author as to editing actions to be taken, and also indicate where changes are anticipated in future versions.</p>
<p>AUTHOR'S NOTE AND QUESTION: Detailed review of this section is solicited, and requirements for any additional configuration control.</p>
<p>The format of the ACL node follows &xep0004;. </p>
<example caption="Configuration Node"><![CDATA[
<items node='urn:xmpp:mix:nodes:config'>
<item id='2016-05-30T09:00:00'>
*** TBS ****
</item>
</items>
]]></example>
</section3>
</section2>
<section2 topic="Non-Standard Nodes" anchor="non-standard-nodes">
<p>
The MIX standard allows channels to use non-standard nodes, using names that do no conflict with the standard nodes. The capabilities of these nodes may be specified in a future XEP or be for private agreement. Non-Standard nodes MUST NOT duplicate or otherwise provide capability that can be provided by standard nodes.
</p>
</section2>
</section1>
<section1 topic='Discovery' anchor='discovery'>
<section2 topic='Discovering a MIX service' anchor='disco-service'>
<p>To determine if a domain hosts a MIX service, a &xep0030; info query should be sent in the usual manner</p>
<example caption="Entity queries a service" ><![CDATA[
<iq from='hag66@shakespeare.example/intibo24'
id='lx09df27'
to='mix.shakespeare.example'
type='get'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
]]></example>
<p>The MIX service then MUST return its identity and the features it supports, which MUST include the 'urn:xmpp:mix:0' feature, and the identity MUST have a category of 'conference' and a type of 'text'. </p>
<example caption="Service responds with Disco Info result" ><![CDATA[
<iq from='mix.shakespeare.example'
id='lx09df27'
to='hag66@shakespeare.example/intibo24'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<identity
category='conference'
name='Shakespearean Chat Service'
type='text'/>
<feature var='urn:xmpp:mix:0'/>
</x>
</query>
</iq>
]]></example>
<p>The result is returned in an extended disco results in a form whose type value is 'urn:xmpp:mix:0#serviceinfo'.
</p>
<p>A MIX service MUST NOT advertise support for &xep0313;, as MAM is supported by the channels and not by the service. A MIX service MUST NOT advertise support for generic &xep0060;, as although MIX makes use of PubSub it is not a generic PubSub service.</p>
</section2>
<section2 topic='Discovering the Channels on a Service' anchor='disco-channel-list'>
<p>The list of channels supported by a MIX service is obtained by a disco#items command. The MIX server MUST only return channel that exist and that the user making the query has rights to subscribe to. This query MAY be made directly by and XMPP client or by a MIX Proxy.</p>
<example caption='MIX Proxy Queries for Channels on MIX Service'><![CDATA[
<iq from='hag66@shakespeare.lit'
id='kl2fax27'
to='mix.shakespeare.lit'
type='get'>
<query xmlns='http://jabber.org/protocol/disco#items'/>
</iq>
]]></example>
<example caption='MIX Service Returns Disco Items Result'><![CDATA[
<iq from='mix.shakespeare.lit'
id='kl2fax27'
to='hag66@shakespeare.lit'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#items'>
<item jid='coven@mix.shakespeare.example' />
<item jid='spells@mix.shakespeare.example' />
<item jid='wizards@mix.shakespeare.example' />
</query>
</iq>
]]></example>
</section2>
<section2 topic='Discovering Channel Information' anchor='disco-channel-info'>
<p>In order to find out more information about a given channel, a user can send a disco#info query to the channel. This query MUST be made by a MIX Proxy and not the end client.</p>
<example caption='Entity Queries for Information about a Specific Channel'><![CDATA[
<iq from='hag66@shakespeare.lit'
id='ik3vs715'
to='coven@mix.shakespeare.lit'
type='get'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
]]></example>
<p>Note that this query comes from the bare JID to the MIX channel, as it will always be sent to the MIX service by a MIX proxy. The channel MUST return its identity and the features it supports. Note that a MIX channel MUST support MAM and so the response will always include both MIX and MAM support.</p>
<example caption='Channel Returns Disco Info Result'><![CDATA[
<iq from='coven@mix.shakespeare.lit'
id='ik3vs715'
to='hag66@shakespeare.lit'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<identity
category='conference'
name='A Dark Cave'
type='mix'/>
<feature var='urn:xmpp:mix:0'/>
<feature var='urn:xmpp:mam:1'/>
</query>
</iq>
]]></example>
</section2>
<section2 topic='Discovering Nodes at a Channel' anchor='disco-channel-nodes'>
<p>Use disco#items to find the nodes associated with a channel. The MIX server MUST only return nodes that exist and that the user making the query has rights to subscribe to. This query MUST be made by a MIX Proxy and not the end client.</p>
<example caption='Entity Queries for Nodes at a Channel'><![CDATA[
<iq from='hag66@shakespeare.lit'
id='kl2fax27'
to='coven@mix.shakespeare.lit'
type='get'>
<query xmlns='http://jabber.org/protocol/disco#items'/>
</iq>
]]></example>
<example caption='Channel Returns Disco Items Result'><![CDATA[
<iq from='coven@mix.shakespeare.lit'
id='kl2fax27'
to='hag66@shakespeare.lit'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#items'>
<item jid='coven@mix.shakespeare.example'
node='urn:xmpp:mix:nodes:presence'/>
<item jid='coven@mix.shakespeare.example'
node='urn:xmpp:mix:nodes:participants'/>
<item jid='coven@mix.shakespeare.example'
node='urn:xmpp:mix:nodes:messages'/>
<item jid='coven@mix.shakespeare.example'
node='urn:xmpp:mix:nodes:subject'/>
<item jid='coven@mix.shakespeare.example'
node='urn:xmpp:mix:nodes:config'/>
</query>
</iq>
]]></example>
</section2>
<section2 topic="Determining Information about a Channel" anchor="find-channel-info">
<p>The Information Node contains various information about the channel that may be useful to the user. This can be read by the XMPP Client directly or by a MIX Proxy.</p>
<example caption='MIX Proxy Requests Channel Information'><![CDATA[
<iq from='hag66@shakespeare.lit'
id='kl2fax27'
to='coven@mix.shakespeare.lit'
type='get'>
<query xmlns='urn:xmpp:mix:0#channel-info'/>
</iq>
]]></example>
<example caption='MIX Service Returns Channel Information'><![CDATA[
<iq from='coven@mix.shakespeare.lit'
id='kl2fax27'
to='hag66@shakespeare.lit'
type='result'>
<query xmlns='urn:xmpp:mix:0#channel-info'>
<name>Witches Coven</name>
<description>A location not far from the blasted heath where the three witches meet</description>
<administrator>
<vCard xmlns='vcard-temp'>
<FN>Hecate</FN>
<TITLE>Chief Witch</TITLE>
</vCard>
</administrator>
<avatar>
<data xmlns='urn:xmpp:avatar:data'>
qANQR1DBwU4DX7jmYZnncm...
</data>
</avatar>
</iq>
]]></example>
</section2>
<section2 topic='Determining the Participants in a Channel' anchor='find-channel-participants'>
<p>
Online clients in the channel are determined from the presence node. Participants in the channel are determined from the Participants Node which will give proxy JID and nick. The jidmap node is used to map to real JIDs. An operation is provided to list channel participants. For JID Hidden channels, only the nicks are returned. For JID Visible channels, nicks and real JIDs are returned.</p>
<example caption='MIX Proxy Requests Participant List'><![CDATA[
<iq from='hag66@shakespeare.lit'
id='kl2fax27'
to='coven@mix.shakespeare.lit'
type='get'>
<query xmlns='urn:xmpp:mix:0#get-participants'/>
</iq>
]]></example>
<example caption='MIX Service Returns Participant List for JID Visible Room'><![CDATA[
<iq from='coven@mix.shakespeare.lit'
id='kl2fax27'
to='hag66@shakespeare.lit'
type='result'>
<query xmlns='urn:xmpp:mix:0#get-participants'>
<items>
<item jid='hag66@shakespeare.lit' nick='thirdwitch'>
<item jid='hag01@shakespeare.lit' nick='top witch'>
</items>
</iq>
]]></example>
</section2>
<section2 topic="Discovering Client MIX Capability" anchor="mix-client-discovery">
<p>
Where a client supports MIX, it MUST advertise this capability in response to a Disco request. This will enable other entities to determine if a client supports MIX. The following example shows a Disco response from a client that supports both MIX and MUC.
</p>
<example caption='Disco Response showing MIX support'><![CDATA[
<iq from='romeo@montague.lit/orchard'
id='disco1'
to='juliet@capulet.lit/chamber'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#info'
node='http://code.google.com/p/exodus#QgayPKawpkPSDYmwT/WM94uAlu0='>
<identity category='client' name='Exodus 0.9.1' type='pc'/>
<feature var='http://jabber.org/protocol/caps'/>
<feature var='http://jabber.org/protocol/disco#info'/>
<feature var='http://jabber.org/protocol/disco#items'/>
<feature var='http://jabber.org/protocol/muc'/>
<feature var='http://jabber.org/protocol/mix'/>
</query>
</iq>
]]></example>
</section2>
</section1>
<section1 topic='Use Cases' anchor='usecases'>
<section2 topic='Common User Use Cases' anchor='usecases-user'>
<section3 topic='Joining a Channel' anchor='usecase-user-join'>
<p>A user joins a channel by sending a MIX "join" command. There is no default set of nodes, so user MUST specify the set of nodes to be subscribed to. To achieve the equivalent service to MUC, a user would subscribe to messages, presence and subject.
This will lead to the server subscribing the user to each of the requested nodes associated with the channel. The MIX server will also add the user to the participant list by injecting a new item into the "urn:xmpp:mix:nodes:participants" node automatically.
</p>
<p>The default MIX model is that only channel participants may subscribe to nodes. A MIX channel MAY allow non-participant subscription. This will be handled by clients directly subscribing to the desired PubSub nodes.</p>
<example caption="User Joins a Channel"><![CDATA[
<iq type='set'
from='hag66@shakespeare.example'
to='coven@mix.shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<join xmlns='urn:xmpp:mix:0'>
<subscribe node='urn:xmpp:mix:nodes:messages'/>
<subscribe node='urn:xmpp:mix:nodes:presence'/>
<subscribe node='urn:xmpp:mix:nodes:participants'/>
<subscribe node='urn:xmpp:mix:nodes:subject'/>
<subscribe node='urn:xmpp:mix:nodes:config'/>
</join>
</iq>
]]></example>
<p>The channel responds with an IQ-result. This stanza includes the nodes to which the user has been successfully subscribed, as well as the bare JID that will be used for the user in this channel and added to the participant list. The following example shows the result of the above request when the request is completed in full. </p>
<example caption="Channel Processes Join Request in Full"><![CDATA[
<iq type='result'
from='coven@mix.shakespeare.example'
to='hag66@shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<join xmlns='urn:xmpp:mix:0' jid='hag66@shakespeare.example'>
<subscribe node='urn:xmpp:mix:nodes:messages'/>
<subscribe node='urn:xmpp:mix:nodes:presence'/>
<subscribe node='urn:xmpp:mix:nodes:participants'/>
<subscribe node='urn:xmpp:mix:nodes:subject'/>
<subscribe node='urn:xmpp:mix:nodes:config'/>
</join>
</iq>
]]></example>
<p>
If a user cannot be subscribed to one or more of the requested nodes (e.g., because the node does not exist), but can be subscribed to some the response simply lists the nodes successfully subscribed. If none of the nodes requested are successfully subscribed to, an error response is sent indicating the reason that the first node requested was not subscribed to. This response will also include other nodes requested where subscription failed for the same reason. The following response example shows a response to the initial request example where
the participant is not be subscribed to all nodes associated with the channel (in this case only messages, participants, and subject).</p>
<example caption="Channel Processes Join With Some Nodes Not Subscribed To"><![CDATA[
<iq type='result'
from='hag66@shakespeare.example'
to='coven@mix.shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<join xmlns='urn:xmpp:mix:0' jid='hag66@shakespeare.example'>
<subscribe node='urn:xmpp:mix:nodes:messages'/>
<subscribe node='urn:xmpp:mix:nodes:participants'/>
<subscribe node='urn:xmpp:mix:nodes:subject'/>
</join>
</iq>
]]></example>
<p>The channel also adds the user to the participants node and sends a notification to subscribers to the participants node.</p>
<example caption="Channel Adds User to Participants Node"><![CDATA[
<message from='coven@mix.shakespeare.example'
to='hecate@shakespeare.example'
id='5A9C7398-DB13-4BFA-A091-2D466C710AAF'>
<event xmlns='http://jabber.org/protocol/pubsub#event'>
<items node='urn:xmpp:mix:nodes:participants'>
<item id='coven+123456@mix.shakespeare.example'>
<participant xmlns='urn:xmpp:mix:0'
nick='thirdwitch'/>
</item>
</items>
</event>
</message>
]]></example>
<p>The user that has been added to the channel is identified by the item id of the item added to the pubsub node, which is the proxy JID of the new channel participant. Each &lt;participant&gt; element will include the nick of the user being added, which will be how the user will typically be shown in the channel.</p>
<p>
Following the MIX server side processing, the user's server will usually add the MIX channel to the user's roster using one way presence. This means that the MIX channel will get presence information from the user. This roster entry will lead to correct handling of the user's presence in the MIX channel. If the user does not wish to publish presence and the channel permits this, then this roster addition does not happen. If the channel requires presence and the user removes the channel from the user's roster, the channel MAY remove the user as a channel participant.
</p>
<p>
A user may subsequently modify subscription to nodes in a channel by sending a subscription modification request, as shown in the following example.
</p>
<example caption="User Modifies Subscription Request"><![CDATA[
<iq type='set'
from='hag66@shakespeare.example'
to='coven@mix.shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<update-subscription xmlns='urn:xmpp:mix:0'>
<subscribe node='urn:xmpp:mix:nodes:messages'/>
</update-subscription>
</iq>
<iq type='result'
from='hag66@shakespeare.example'
to='coven@mix.shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<update-subscription xmlns='urn:xmpp:mix:0' jid='hag66@shakespeare.example'>
<subscribe node='urn:xmpp:mix:nodes:messages'/>
</update-subscription>
</iq>
]]></example>
</section3>
<section3 topic="User Preferences and Additional Information" anchor="usecase-visibilty-pref">
<p>A channel MAY store user preferences and parameters with each user. There are two preference options.
</p>
<p>
A user JID visibility preference have the following values:
</p>
<ol>
<li>'Default'. In this setting, the channel default value will be used. This value is used if another value is not explicitly set.</li>
<li>'Never'. If this is set, JID will never be shared and user will be removed from the channel if its mode changes to JID-visible-mandatory.</li>
<li>'Prefer Not'. If this is set, JID will only be shared if mode is JID-visible-mandatory.</li>
</ol>
<p>
The user may specify that no Private Messages are to be sent from the channel, and allow vCard retrieval.
</p>
<p>
The following table sets out the standardized user preference values. A MIX implementation may use other values.
</p>
<table caption="Standard User Preference Options">
<tr><th>Option</th> <th>Values</th><th>Default</th></tr>
<tr><td>'JID Visibility'</td> <td>'Default', 'Never', 'Prefer Not'</td> <td>'Use Channel Default'</td></tr>
<tr><td>'Private Messages'</td><td>'Allow', 'Block'</td> <td>'Allow'</td></tr>
<tr><td>'vCard'</td><td>'Allow', 'Block'</td> <td>'Block'</td></tr>
</table>
<p>When joining a channel, the client may specify one or more preference options as a &xep0004; form. In the response, the server MUST specify all of the user preferences supported by the server, with default values if the user has not requested a different value. The following example shows joining a channel and setting a preference.</p>
<example caption="User Joins a Channel and Specifies a preference"><![CDATA[
<iq type='set'
from='hag66@shakespeare.example'
to='coven@mix.shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<join xmlns='urn:xmpp:mix:0'>
<subscribe node='urn:xmpp:mix:nodes:messages'/>
<subscribe node='urn:xmpp:mix:nodes:presence'/>
<x xmlns='jabber:x:data' type='submit'>
<field var='FORM_TYPE' type='hidden'>
<value>urn:xmpp:mix:0</value>
</field>
<field var='JID Visibility'>
<value>Never</value>
</field>
</x>
</join>
</iq>
]]></example>
<p>The following example shows a successful join, which also reports all the user preferences. </p>
<example caption="Channel Successfully Processes Join and returns the preferences set"><![CDATA[
<iq type='result'
from='coven@mix.shakespeare.example'
to='hag66@shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<join xmlns='urn:xmpp:mix:0' jid='hag66@shakespeare.example'>
<subscribe node='urn:xmpp:mix:nodes:messages'/>
<subscribe node='urn:xmpp:mix:nodes:presence'/>
<x xmlns='jabber:x:data' type='result'>
<field var='FORM_TYPE' type='hidden'>
<value>urn:xmpp:mix:0</value>
</field>
<field var='JID Visibility'>
<value>Never</value>
</field>
<field var='Private Messages'>
<value>Allow</value>
</field>
<field var='vCard'>
<value>Block</value>
</field>
</x>
</join>
</iq>
]]></example>
<p>The client may also query the channel in order to find out which user preferences are supported and the options available. This will allow users to set options not specified in the standard. The result is a form template.</p>
<example caption="User Requests and Recieves Preferences Template Form"><![CDATA[
<iq type='set'
from='hag66@shakespeare.example'
to='coven@mix.shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<user-preference xmlns='urn:xmpp:mix:0'/>
<x xmlns='jabber:x:data' type='submit'>
<field var='FORM_TYPE' type='hidden'>
<value>urn:xmpp:mix:0</value>
</field>
<field var='JID Visibility'>
<value>Never</value>
</field>
<field var='Private Messages'>
<value>Allow</value>
</field>
<field var='vCard'>
<value>Block</value>
</field>
</x>
</iq>
<iq type='result'
from='coven@mix.shakespeare.example'
to='hag66@shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<user-preference xmlns='urn:xmpp:mix:0'>
<x xmlns='jabber:x:data' type='result'>
<field var='FORM_TYPE' type='hidden'>
<value>urn:xmpp:mix:0</value>
</field>
<field var='JID Visibility'>
<value>Never</value>
</field>
<field var='Private Messages'>
<value>Allow</value>
</field>
<field var='vCard'>
<value>Block</value>
</field>
</x>
</user-preference>
</iq>
]]></example>
<p>
A user may modify preferences using the corresponding set operation.
</p>
<example caption="User Updates Preferences"><![CDATA[
<iq type='get'
from='hag66@shakespeare.example'
to='coven@mix.shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<user-preference xmlns='urn:xmpp:mix:0'/>
</iq>
<iq type='result'
from='coven@mix.shakespeare.example'
to='hag66@shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<user-preference xmlns='urn:xmpp:mix:0'>
<x xmlns='jabber:x:data' type='form'>
<field var='FORM_TYPE' type='hidden'>
<value>urn:xmpp:mix:0</value>
</field>
<field type='list-single' label='Preference for JID Visibility' var='JID Visibility'>
<option label='JID Never Shown'><value>Never</value></option>
<option label='Default Behaviour'><value>Default</value></option>
<option label='Try not to show JID'><value>Prefer Not</value></option>
</field>
<field type='list-single' label='Example Custom Preference' var='Custom Preference'>
<option label='One Option'><value>A</value></option>
<option label='Another Option'><value>B</value></option>
</field>
</x>
</user-preference>
</iq>
]]></example>
</section3>
<section3 topic='Leaving a Channel' anchor='usecase-user-leaving'>
<p>Users generally remain in a channel for an extended period of time. In particular the user remains as a participant the channel does not change when the user goes offline as happens with &xep0045;. So, leaving the channel is a permanent action for a user across all clients, not just a matter of telling the channel that the user is not currently available or for a single client. In order to leave a channel, a user sends a MIX "leave" command to the channel. When a user leaves the channel, the user's client will remove the channel from the user's roster.</p>
<example caption="User Leaves a Channel"><![CDATA[
<iq type='set'
from='hag66@shakespeare.example'
to='coven@mix.shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<leave xmlns='urn:xmpp:mix:0'/>
</iq>
]]></example>
<p>When the user leaves the channel, the MIX service is responsible for unsubscribing the user from all nodes in the channel and for removing the user from the participants and presence list. If the user has online presence when the user leaves the channel, the change of presence status caused by removing the user's entry or entries from the presence node will ensure that subscribers to the presence node are correctly updated on presence status.
Deletion from the participants and presence functions as if the item (channel participant) had been deleted using the PubSub retract mechanism with notification set to true. Notification of the deletion is sent to clients subscribed to the participants PubSub nodes, as shown in the example below.
</p>
<example caption="Reporting when User Leaves a Channel"><![CDATA[
<message from='coven@mix.shakespeare.example' to='hecate@shakespeare.example' id='foo'>
<event xmlns='http://jabber.org/protocol/pubsub#event'>
<items node='urn:xmpp:mix:nodes:participants'>
<retract id='coven+123456@mix.shakespeare.example'/>
</items>
</event>
</message>
<message from='coven@mix.shakespeare.example' to='hecate@shakespeare.example' id='bar'>
<event xmlns='http://jabber.org/protocol/pubsub#event'>
<items node='urn:xmpp:mix:nodes:presence'>
<retract id='coven+123456@mix.shakespeare.example/8765'/>
</items>
</event>
</message>
]]></example>
</section3>
<section3 topic="Setting a Nick" anchor="usecase-setting-nick">
<p>
Each participant of a channel may have a nick, which is how other users in the channel will see the user. In some cases a nick is not needed, for example where a user reads messages in a channel but does not send messages or share presence information. A nick MUST be present for a user to send a message to a channel or for a user's presence to be shared on a channel. There are four ways that a user's nick can be obtained. The choice of mechanism or mechanisms is dependent on channel policy:
</p>
<ol>
<li>The nick is registered with the user account in some way, for example as part of user provisioning with nick configured as an attribute in a directory service. This may be chosen by corporate services that wish to ensure consistent nick values for a set of users and channels.</li>
<li>The nick is registered with the MIX service, as described in <link url='#usecase-user-register'> Registering a Nick </link>.</li>
<li>The user explicitly sets the nick, as described in this section.</li>
<li>The MIX service generates the nick. In this case it is recommended that the assigned nick is a UUID following &rfc4122;.</li>
</ol>
<p>
A user will typically set a nick when joining a channel and may update this nick from time to time. The user does this by sending a command to the channel to set the nick. If the user wishes the channel to assign a nick (or knows that the channel will assign a nick) the nick field can be left blank, so that the user can see what is assigned in the result.
</p>
<example caption="User sets Nick on Channel"><![CDATA[
<iq type='set'
from='hag66@shakespeare.example'
to='coven@mix.shakespeare.example'
id='7nve413p'>
<query xmlns='urn:xmpp:mix:0'>
<nick>thirdwitch</nick>
</query>
</iq>
]]></example>
<p>
The channel will return the nick that is to be used, noting that this may be different to the requested nick. MIX services SHOULD apply the "nickname" profile of the PRECIS OpaqueString class, as defined in &rfc7700;.
</p>
<example caption="Channel informs user of Nick"><![CDATA[
<iq type='result'
from='hag66@shakespeare.example'
to='coven@mix.shakespeare.example'
id='7nve413p'>
<query xmlns='urn:xmpp:mix:0'>
<nick>thirdwitch</nick>
</query>
</iq>
]]></example>
</section3>
<section3 topic='Registering a Nick' anchor='usecase-user-register'>
<p>A user can register a nick with the MIX service. Nick registration can be used ensure that a user is able to use the same nick in all channels in the service and to prevent other users from using a registered nick. This can help achieve a consistent experience across a set of channels and prevent user confusion. Support for nick registration by a MIX service is optional. Where nick registration is supported, nick registration may be optional or mandatory.
Where a user has registered a Nick with the MIX service, it may be used by each channel according to policy for the channel. A nick is associated with the user's bare JID.
</p>
<p>
In order to determine if a Nick may be registered, the user may use disco to determine capabilities of the MIX service.
</p>
<example caption="User Determines features of the MIX service"><![CDATA[
<iq type='get'
from='hag66@shakespeare.example'
to='mix.shakespeare.example'
id='7nve413p'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
]]></example>
<p>
The response will be a list of features of the MIX channel. If Nick Registration is supported, then the result set will include &lt;feature var="mix_nick_register"/&gt;.
</p>
<p>
To register a nick with the MIX service the user sends
a &lt;register/&gt; command to the service. </p>
<example caption="User Registers with Service"><![CDATA[
<iq type='set'
from='hag66@shakespeare.example'
to='mix.shakespeare.example'
id='7nve413p'>
<register xmlns='urn:xmpp:mix:0'>
<nick>thirdwitch</nick>
</register>
</iq>
]]></example>
<p>On success, the service informs the user of its nick. The nick that is issued might be different from the nick that was requested, for example if the service completes normalization of nicknames for purposes of internationalization.</p>
<p>
MIX services SHOULD apply the "nickname" profile of the PRECIS OpaqueString class, as defined in &rfc7700;.
</p>
<example caption="Service Returns User of Nick"><![CDATA[
<iq type='result'
to='mix.shakespeare.example'
from='hag66@shakespeare.example'
id='7nve413p'>
<register xmlns='urn:xmpp:mix:0'>
<nick>thirdwitch</nick>
</register>
</iq>
]]></example>
<p>If the requested nick is already taken, the MIX service returns a &lt;conflict/&gt; error:</p>
<example caption="Nick is Taken">
<![CDATA[<iq type='error'
to='mix.shakespeare.example'
from='hag66@shakespeare.example'
id='7nve413p'>
<error type='cancel'>
<conflict xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/>
</error>
</iq>
]]></example>
<p>If the register request does not contain a &lt;nick/&gt; element, then the MIX service assigns one. It is recommended that the assigned nick is a UUID following &rfc4122;.
</p>
</section3>
<section3 topic='Setting User Presence' anchor='usecase-user-presence'>
<p>
A user joins a channel over an extended period, and participation in a channel does not generally change when user goes online or offline. The user's participation in a channel is reflected by the user's bare JID in the participant node. All messages to the channel are sent to this JID.
</p>
<p>
A user may share presence information with the channel, for one or more online clients. Where a user shares presence information with a channel, the channel is entered by the user's server into the user's roster when the user subscribes to the channel. When an XMPP client comes online or changes presence status, this will be communicated by the user to the user's server using broadcast presence. The user's XMPP server is then responsible to share this presence information to each entry in the roster and in particular to each MIX channel in the roster. The MIX channel will update the "urn:xmpp:mix:nodes:presence" node with any change of status and the updated presence information and then share this updated presence with users subscribed to this node, as described below. When the user sets an explicit status, this is used to modify the presence node in the channel. When a client being used by the user goes offline, the associated server will send presence status "unavailable" to the MIX channel, which will cause the full JID for that client to be removed from the presence node.
</p>
<p>
A channel may require that all channel participants share presence information with the channel, which is represented in the "urn:xmpp:mix:nodes:presence" node. If sharing presences is required by the channel, an XMPP client conforming to this specification SHALL share presence with the channel by including the channel in the user's roster. Note that the MIX server cannot generally enforce this, but it can require and enforce that when a message is sent to the channel, that the sender of the message is in the presence list.
</p>
<p>
Presence status and availability is set in a MIX channel by standard presence stanzas sent to the MIX channel by the user's server. User's wishing to receive presence updates will subscribe to the MIX channel presence node. Presence updates are sent out to subscribing using standard XEP-0045 compatible presence stanzas.
</p>
<p>
A user setting status is now used as an example. Unlike in &xep0045; where coming online is a special action, coming online in MIX is implicit when presence status is set. Going offline is a achieved by setting presence status to unavailable, which removes the client full JID entry from the presence node. When a user sets a presence status, the user's server sends updated presence to the MIX channel, and the MIX server then publishes the user's availability to the "urn:xmpp:mix:nodes:presence" node. If there is not an item named by the full JID of the client with updated presence status, this item is created. If there is not an item named by the full JID of the client with updated presence status, then an item is created.</p>
<example caption="User Setting Presence Status">
<![CDATA[<presence xmlns='jabber:client' from=‘hag66@shakespeare.example/pda’ to='coven@mix.shakespeare.example'>
<show>dnd</show>
<status>Making a Brew</status>
</presence>]]></example>
<p>The user's presence information is then published by the service to the "urn:xmpp:mix:nodes:presence" node, with the 'publisher' attribute set to the user's participant identifier (the proxy JID. The MIX channel then broadcasts the presence change to all users who are subscribed to the "urn:xmpp:mix:nodes:presence" node. The presence stanza is sent from the proxy (anonymized) full JID of the user.
Note that presence is associated with a client and so will have a full JID as it comes directly from the client and not through the MIX Proxy.</p>
<example caption="Channel Distributes Presence">
<![CDATA[<presence from='coven+123435@mix.shakespeare.example/678'
to='coven@mix.shakespeare.example'
id='77E07BB0-55CF-4BD4-890E-3F7C0E686BBD'>
<nick xmlns='http://jabber.org/protocol/nick'>thirdwitch</nick>
<show>dnd</show>
<status>Making a Brew</status>
</presence>]]></example>
<p>
The presence is distributed to those subscribing to the MIX channel presence node using a standard XMPP presence stanza. The presence change is recorded on the "urn:xmpp:mix:nodes:presence" node in the item for the full JID of the client to which the presence relates. The history of this node will be held as PubSub format in the MAM archive, so that presence history may be viewed.
</p>
</section3>
<section3 topic="Coming Online: Obtaining Presence" anchor="usecase-obtaining-presence">
<p>
The presence information for a channel is stored in the urn:xmpp:mix:nodes:presence node and distributed using standard presence stanzas to users subscribing to this presence node. The user's server will then pass this presence information on to all online clients. When a client goes offline, it will lose synchronization with the presence node. When the client comes online, the clients server will send a directed presence stanza to the MIX channel. This will happen as a consequence of the MIX channel being in the user's roster and the MIX channel sending a presence update to the MIX channel. When the MIX channel adds or modifies presence for a client to the roster, this presence change will be distributed to all users subscribing to the presence node.
</p>
<p>
When the full JID of a client is added to the MIX channel presence node and that full JID is not in the presence list, the MIX channel will send to the client presence for all of the items in the presence node using standard presence stanzas. This will give the client full current presence.
</p>
</section3>
<section3 topic="Determining Real JIDs" anchor="usecase-real-jids">
<p>
Presence information will provide a MIX client with the nicks and anonymized proxy JIDs for participants. For JID visible rooms, the user may look up the real JID using the "urn:xmpp:mix:nodes:jidmap" node. The items in this node are identified by proxy JID, and so the real JID can be retrieved using a straightforward PubSub query. While a user may subscribe to the jidmap node, it is more likely to be used to directly look up JIDs as and when needed.
</p>
</section3>
<section3 topic="Coming Online: Synchronizing Message History" anchor="usecase-sync-history">
<p>
A MIX client will typically display message history of the channel to the user. When a client comes online it will need to obtain this message history from the MAM archive associated with the channel. There are three basic approaches a client will take:
</p>
<ol>
<li>If the client has previously displayed message history and has been offline for a reasonably small time, the client will wish to retrieve all messages since the last one displayed to the user.</li>
<li>The client may wish to display a fixed number of messages, perhaps finding more messages if the client subsequently requests.</li>
<li>The client may wish to display messages from a recent time period, perhaps finding more messages if the client subsequently requests.</li>
</ol>
<p>AUTHOR'S NOTE: Examples to be added</p>
</section3>
<section3 topic='Going Offline' anchor='usecase-user-offline'>
<p>When a client goes offline, this presence update is sent by the client's server to the MIX channel. From the client perspective, this is the same as any other presence change. Handling by the MIX channel is slightly different.</p>
<example caption="Client Goes Offline in the Channel"><![CDATA[
<presence type='unavailable'
from='hag66@shakespeare.example/pda'
to='coven@mix.shakespeare.example'/>
]]></example>
<p>The MIX channel will retract (remove) the item in the presence node of the MIX channel identified by the client's full JID. The MIX channel will notify subscribers to the presence node of the user going offline by sending a presence stanza to the full proxy JID of each client.</p>
<example caption="Channel Distributes Notification of Client going Offline">
<![CDATA[<presence from='coven+12345@mix.shakespeare.example/678'
to='hecate@shakespeare.example'
id='77E07BB0-55CF-4BD4-890E-3F7C0E686BBD'
type='unavailable'/>]]></example>
<p>
There is the possibility that the message associated with the user going offline will be lost. If this happens, "ghost" entries will appear in the presence node. A MIX server may take steps to address this, for example by probing client with a disco for presence items that remain unchanged for a long period.
</p>
<p>
It is desirable to prevent clients from going offline briefly and then coming back online again, as this will lead to "flapping presence". The recommended approach to achieve this is use of &xep0198; to maintain an XMPP client connection in the event of short term TCP failure.
</p>
</section3>
<section3 topic='Sending a Message' anchor='usecase-user-message'>
<p>A client sends a message directly to a MIX channel as a standard groupchat message, in exactly the same way as for &xep0045;. Messages are sent directly to the channel and do not use the MIX Proxy. </p>
<example caption="User Sends Message to Channel"><![CDATA[
<message from='hag66@shakespeare.example/pda'
to='coven@mix.shakespeare.example'
id='92vax143g'
type='groupchat'>
<body>Harpier cries: 'tis time, 'tis time.</body>
</message>
]]></example>
<p>The MIX channel then puts a copy of the message into the MAM archive for the channel and sends a copy of the message to each participant in
standard groupchat format. These messages sent by the channel are addressed to the bare JID of each participant and this will be handled by the participant's MIX Proxy. The message from value is the full Proxy JID of the message sender. The id of the message is the ID from the MAM archive.</p>
<example caption="Channel Reflects Message to Participants"><![CDATA[
<message from='coven+12345@mix.shakespeare.example/678'
to='hecate@shakespeare.example'
id='77E07BB0-55CF-4BD4-890E-3F7C0E686BBD'
type='groupchat'>
<body>Harpier cries: 'tis time, 'tis time.</body>
</message>
]]></example>
<p>
The messages sent to participants have a different message id to the originally submitted message. This does not impact most recipients, but it does not allow the message originator to correlate the message with the submitted message. To address this the MIX channel MUST include an additional element of the message copy going back to the originator's bare JID that includes the original id. This enables the originator to correlate the received message with the message submitted.
</p>
<example caption="Channel Reflects Message back to Originator"><![CDATA[
<message from='coven+12345@mix.shakespeare.example/678'
to='hag66@shakespeare.example'
id='77E07BB0-55CF-4BD4-890E-3F7C0E686BBD'
type='groupchat'>
<body>Harpier cries: 'tis time, 'tis time.</body>
<submission-id xmlns='urn:xmpp:mix:0'>92vax143g</submission-id>
</message>
]]></example>
</section3>
<section3 topic="Retracting a Message" anchor="usecase-retract">
<p>
A MIX channel MAY support message retraction, where the sender of a messages deletes a messages from the message history and optionally replace it with another message. This retraction mechanism will be based on the &xep0060; retract operation. A client looking at message history may choose to look at "current state" which will show status after the retraction or "full history" which will include the message that was retracted.
</p>
<p>
AUTHOR'S NOTE: Define new protocol to support this and add example.
</p>
</section3>
<section3 topic="Setting the Channel Subject" anchor="set-subject">
<p>
Setting the subject for a channel follows a similar procedure to sending a message. An XMPP client will send a message setting the subject directly to the MIX channel.
</p>
<example caption="User Sets Channel Subject"><![CDATA[
<message from='hag66@shakespeare.example/pda'
to='coven@mix.shakespeare.example'
id='92vax143g'
type='groupchat'>
<subject>
<item>
<text xml:lang="en">How to use Toads</text>
<text xml:lang="de">Wie benutzt man Kröten</text>
</item>
</subject>
</message>
]]></example>
<p>
This message is received by the MIX channel, which will set the Subject Node for the channel, and then distribute the message to participants that are subscribed to the Subject Node, with the message addressed to the MIX Proxy.
</p>
<example caption="Channel Reflects New Subject to Participants"><![CDATA[
<message from='coven+12345@mix.shakespeare.example/678'
to='hecate@shakespeare.example'
id='77E07BB0-55CF-4BD4-890E-3F7C0E686BBD'
type='groupchat'>
<subject>
<item>
<text xml:lang="en">How to use Toads</text>
<text xml:lang="de">Wie benutzt man Kröten</text>
</item>
</subject>
</message>
]]></example>
<p>
When a new Participant joins a channel and subscribes to the Subject Node, the channel MUST send to the user's MIX Proxy a message with the current subject. An XMPP Client MAY directly read the Subject node using &xep0060;.
</p>
</section3>
<section3 topic='Telling another User about a Channel' anchor='usecase-user-tell'>
<p>
A convenient way to reference another channel is to use &xep0372; which enables the JID of a channel to be shared. This might be used simply to inform the message recipient about the channel or as mechanism to invite the user to join the channel. This is useful as an invitation mechanism to a channel that any user can join or where the invitee knows that the user may join (e.g., because the channel is for all users in an organization).
</p>
</section3>
<section3 topic='Inviting another User to join a Channel that the user does not have Permission to Join' anchor='usecase-user-invite'>
<p> Invitation by reference, as described in the previous section, is a convenient approach to invite a user to join a channel that the user has permission to join. This section describes the approach used when the inviter has permission to grant rights for the invitee to become a channel participant. This might be because the inviter is an administrator of the channel or the channel may have a special mode where channel participants may grant rights for other users to join a channel ('Participation Addition by Invitation from Participant' enabled). This approach is used to avoid cluttering the allowed node with JIDs of users who are invited to join, but do not accept the invitation.
When a channel participant(the inviter) invites another user (the invitee) to join a channel, the following sequence of steps is followed:
</p>
<ol>
<li>The channel inviter sends to the channel requesting an invite for the invitee.</li>
<li>The channel sends an invitation to the inviter.</li>
<li>The inviter sends the invitation to the invitee.</li>
<li>The invitee MAY use the invitation to join the channel.</li>
<li>The invitee MAY send a response to the inviter, indicating if the invitation was accepted or declined.</li>
</ol>
<p>
The first step is for the inviter to request an invitation from the channel. The invitation contains inviter, invitee and a token. The channel will evaluate if the inviter has rights to issue the invitation. This will be because the inviter is a channel administrator or if the inviter is a channel participant and the channel has 'Participation Addition by Invitation from Participant' mode enable. If the inviter has rights to make the invitation, the channel will return a token. The token is a string that the channel can subsequently use to validate an invitation. The format of the token is not specified in this standard. The encoded token MAY reflect a validity time.
</p>
<example caption='Inviter Requests and Receives Invitation'><![CDATA[
<iq from='hag66@shakespeare.lit/pda'
id='kl2fax27'
to='coven@mix.shakespeare.lit'
type='get'>
<query xmlns='urn:xmpp:mix:0#request-invitation'/>
<invitee>cat@shakespeare.lit</invitee>
</iq>
<iq from='coven@mix.shakespeare.lit'
id='kl2fax27'
to='hag66@shakespeare.lit/pda'
type='result'>
<query xmlns='urn:xmpp:mix:0#request-invitation'>
<invitation>
<inviter>hag66@shakespeare.lit</inviter>
<invitee>cat@shakespeare.lit</invitee>
<channel>coven@mix.shakespeare.lit</channel>
<token>ABCDEF</token>
</invitation>
</iq>
]]></example>
<p>
The inviter can now send the invitee a message containing the invitation, as shown in the following example.
</p>
<example caption='Inviter sends Invitation to Invitee'><![CDATA[
<message from='hag66@shakespeare.lit/pda'
id='foo'
to='cat@shakespeare.lit'>
<body>Would you like to join the coven?<body>
<invitation xmlns='urn:xmpp:mix:0'>
<inviter>hag66@shakespeare.lit</inviter>
<invitee>cat@shakespeare.lit</invitee>
<channel>coven@mix.shakespeare.lit</channel>
<token>ABCDEF</token>
</invitation>
</iq>
]]></example>
<p>The invitation can now be used by the invitee to join a channel. The invitation is simply added to the standard channel join, so that the channel can validate the invitation using the token. If the allowed node is present and the invitee is not matched against any item, the channel MUST add the invitee to the allowed node as part of the join.</p>
<example caption="User Joins a Channel with an Invitation"><![CDATA[
<iq type='set'
from='cat@shakespeare.example'
to='coven@mix.shakespeare.example'
id='E6E10350-76CF-40C6-B91B-1EA08C332FC7'>
<join xmlns='urn:xmpp:mix:0'>
<subscribe node='urn:xmpp:mix:nodes:messages'/>
<invitation>
<inviter>hag66@shakespeare.lit</inviter>
<invitee>cat@shakespeare.lit</invitee>
<channel>coven@mix.shakespeare.lit</channel>
<token>ABCDEF</token>
</invitation>
</join>
</iq>
]]></example>
<p>The invitee may send an acknowledgement back to the inviter, noting the status of the invitation. Values are:</p>
<ul>
<li>'Joined': The invitee has joined the channel.</li>
<li>'Declined': The invitee is not taking up the invitation.</li>
<li>'Acknowledged': The invitation is acknowledged, without information on action taken or planned.</li>
</ul>
<example caption='Invitee sends Acknowledgement to Inviter'><![CDATA[
<message from='cat@shakespeare.lit/miaow'
id='bar'
to='hag66@shakespeare.lit/pda'>
<body>No Thanks - too busy chasing mice....<body>
<invitation-ack xmlns='urn:xmpp:mix:0'>
<value>Declined</value>
<invitation>
<inviter>hag66@shakespeare.lit</inviter>
<invitee>cat@shakespeare.lit</invitee>
<channel>coven@mix.shakespeare.lit</channel>
<token>ABCDEF</token>
</invitation>
</invitation-ack>
</iq>
]]></example>
</section3>
<section3 topic='Sending Private Messages' anchor='usecase-user-private-messages'>
<p>
Private Messages are used to provide communication with another channel participant through the MIX channel, without the initiating user knowing the real JID of the channel participant. A channel MAY support use of Private Messages. Private messages are standard XMPP messages. A message goes through a number of stages with different addressing. This is set out in the following table.
</p>
<table caption="Setting From and To when sending Private Messages">
<tr><th>Message</th><th>From</th><th>To</th></tr>
<tr><td>First Message from Client to MIX Channel</td><td>Full JID of initiator's client</td><td>Proxy bare JID of responder</td></tr>
<tr><td>First Message from MIX Channel to responder's MIX Proxy</td><td>Proxy full JID of initiator's client</td><td>Bare JID of responder</td></tr>
<tr><td>First Message from responder's MIX Proxy to one or more of the responder's clients</td><td>Proxy full JID of initiator</td><td>Full JID of responder's client</td></tr>
<tr><td>Messages from responder's client to MIX Channel</td><td>Full JID of responder's client</td><td>Proxy full JID of initiator's client</td></tr>
<tr><td>Messages from MIX channel to initiator's client</td><td>Proxy full JID of responder's client</td><td>Full JID of initiator's client</td></tr>
<tr><td>Messages from initiator's client to MIX Channel</td><td>Full JID of initiator's client</td><td>Proxy full JID of responder's client</td></tr>
<tr><td>Message from MIX Channel to responder's client</td><td>Proxy full JID of initiator's client</td><td>Full JID of responder's client</td></tr>
</table>
<p>Private Messages MAY be archived using MAM by the XMPP servers associated with initiator and responder. Private Messages MUST NOT be archived by the MIX channel.</p>
</section3>
<section3 topic="Requesting vCard" anchor="usecase-vcard">
<p>A user may request the vCard of a channel participant by sending a request through the channel. The request may be sent directly by the client or through a MIX Proxy. The MIX channel MAY pass this request on or may block it. In the following example, the requesting client sends a message to the anonymized bare JID of the channel participant for which the vCard is desired.</p>
<example caption="Client directly requests vCard through channel" ><![CDATA[
<iq from='hag66@shakespeare.example/intibo24'
id='lx09df27'
to='coven+989898@mix.shakespeare.example'
type='get'>
<vCard xmlns='vcard-temp'/>
</iq>
]]></example>
<p>The MIX channel MAY pass on the vCard request or may reject with an error, dependent on channel policy. The MIX service will then address the vCard request to the MIX proxy (bare JID) using an anonymous full proxy JID to hide the requester. </p>
<example caption="Channel passes on vCard request to MIX Proxy" ><![CDATA[
<iq from='coven+123456@mix.shakespeare.example/6789'
id='lx09df27'
to='peter@shakespeare.lit'
type='get'>
<vCard xmlns='vcard-temp'/>
</iq>
]]></example>
<p>
The MIX Proxy, on behalf of the user, MAY send a response or reject with an error. The MIX Proxy will send the vCard back to the channel.
</p>
<example caption="Service responds with Disco Info result" ><![CDATA[
<iq from='peter@shakespeare.lit'
id='lx09df27'
to='coven+123456@mix.shakespeare.example/6789'
type='result'>
<vCard xmlns='vcard-temp'>
<FN>Peter Saint-Andre</FN>
<N>
<FAMILY>Saint-Andre</FAMILY>
<GIVEN>Peter</GIVEN>
<MIDDLE/>
</N>
<NICKNAME>stpeter</NICKNAME>
<URL>http://www.xmpp.org/xsf/people/stpeter.shtml</URL>
</vCard>
<query xmlns='http://jabber.org/protocol/disco#info'>
</iq>
]]></example>
<p>
The MIX channel will then send the vCard response to the requesting client on behalf of the client sending the response.
</p>
<example caption="Service responds with Disco Info result" ><![CDATA[
<iq from='coven+989898@mix.shakespeare.example'
id='lx09df27'
to='hag66@shakespeare.example/intibo24'
type='result'>
<vCard xmlns='vcard-temp'>
<FN>Peter Saint-Andre</FN>
<N>
<FAMILY>Saint-Andre</FAMILY>
<GIVEN>Peter</GIVEN>
<MIDDLE/>
</N>
<NICKNAME>stpeter</NICKNAME>
<URL>http://www.xmpp.org/xsf/people/stpeter.shtml</URL>
</vCard>
</iq>
]]></example>
</section3>
</section2>
<section2 topic="Use of MAM" anchor="use-mam">
<p>
All nodes of each MIX channel are archived using MAM. Access to history in these nodes uses standard MAM protocol to access the channel nodes and to retrieve information from the nodes. Information retrieved using MAM will be of the format stored on the node and will include &xep0060; PubSub wrapping. MAM is the MIX mechanism to get at this information, in preference to direct use of PubSub.
</p>
<p>
AUTHOR'S NOTE: Add example of message retrieved using MAM, showing XEP-0060 wrapping
</p>
<p>
There are XEPs that extend MAM and in some cases modify core MAM requirements. Such XEPs may be used in conjunction with MAM, provided that they are supported by the MIX channel. If such XEPs are used, the requirements specified MUST be followed.
</p>
<p>
PubSub provides the ability to modify the state of the node, and distinguishes between current state and full history. It is anticipated that MAM will be extended with an option to choose between "current state" and "full history". This capability will be useful for and used by MIX.
</p>
<p>
AUTHOR'S NOTE: This specification will be updated to reference this MAM extension when it is written.
</p>
</section2>
<section2 topic='Administrative Use Cases' anchor='usecases-admin'>
<section3 topic='Checking For Permission To Create a Channel' anchor='usecase-admin-check-create'>
<p>
MIX does not standardize an access control model for creating and deleting MIX channels. The choice is left to the MIX implementer, and could be a very simple or complex approach.
</p>
<p>
AUTHOR'S NOTE: MIX Protocol to be added to create channel; check for permission to create channel; delete channel
</p>
<example caption="" ><![CDATA[
]]></example>
</section3>
<section3 topic='Creating a Channel' anchor='usecase-admin-create'>
<p>
AUTHOR'S NOTE: Dave Cridland has suggested the following protocol.
<![CDATA[
<iq to='mix.cridland.im' type='set'>
<create channel='some-room-here@mix.cridland.im' xmlns='urn:xmpp:mix:0'>
<optional-configuration-form/>
</create>
</iq>
]]>
</p>
<example caption="" ><![CDATA[
]]></example>
</section3>
<section3 topic='Creating a Channel for Ad Hoc User' anchor='usecase-admin-create-adhoc'>
<p>
Rooms may be created for ad hoc use between a set of users. Channels of this nature will have channel name created by the server and will not be addressable or discoverable.
</p>
<example caption="" ><![CDATA[
]]></example>
</section3>
<section3 topic='Configuring a Channel' anchor='usecase-admin-'>
<p>
Channel jid is set on channel creation and may not be changed. All other channel may be changed if channel configuration allows.
</p>
<p>
AUTHOR'S NOTE: Allow configuration by direct writes to 'urn:xmpp:mix:nodes:config' . Also specify MIX XEP-0004 commands to achieve this.
</p>
<example caption="" ><![CDATA[
]]></example>
</section3>
<section3 topic='Destroying a Channel' anchor='usecase-admin-destroy'>
<p>
MIX channels are always explicitly destroyed by an owner of the channel or by a server operator. There is no concept of temporary channel, equivalent to &xep0045; temporary room which is automatically destroyed by the server when the users leave. However, channels may be configured with an explicit lifetime, after which the channel MUST be removed by the MIX server. Where a channel is created for ad hoc use, it may be desirable to keep the channel for history reference or for re-use by the same set of users.
</p>
<p>Note that the owner of the channel does not need to have presence registered in the channel in order to destroy it.</p>
<p>
AUTHOR'S NOTE: More TBS
</p>
<example caption="" ><![CDATA[
]]></example>
</section3>
<section3 topic='Server Destroying a Channel' anchor='usecase-server-destroy'>
<p>
Servers may destroy channels which have no participants and/or presence according to local policy. There will often be good reasons to not destroy rooms in these scenarios.
</p>
</section3>
<section3 topic='Modifying User Affiliations' anchor='usecase-admin-affiliations'>
<p></p>
<example caption="" ><![CDATA[
]]></example>
</section3>
<section3 topic='Removing a User From a Channel (Kicking)' anchor='usecase-admin-kick'>
<p></p>
<example caption="" ><![CDATA[
]]></example>
</section3>
</section2>
</section1>
<section1 topic="Supporting MIX and MUC together" anchor="mix-and-muc-together">
<p>
MIX is specified as a service that can be used independent of MUC and a MIX service may be implemented without MUC. If both MIX and MUC are implemented, three approaches are noted.
</p>
<ol>
<li>Entirely separate MIX and MUC implementation, with MIX and MUC using separate domains and MIX channels being completely separate from MUC rooms.</li>
<li>Fully integrated MIX and MUC implementation, with MIX and MUC sharing a single domain and rooms/channels equivalent.</li>
<li>Partially integrated MIX and MUC implementation, with MIX and MUC using separate domains, but rooms/channel are common. This means that each MIX channel will have MUC room of the same name and same participants.</li>
</ol>
<p>The fully integrated approach would be transparent to clients. Disco of a room or channel would show support for both MUC and MIX, which would enable a client to choose whether to use MUC or MIX. The following example shows how a MIX service that also supported MUC would respond:</p>
<example caption="Service responds with Disco Info result showing MIX and MUC support" ><![CDATA[
<iq from='mix.shakespeare.example'
id='lx09df27'
to='hag66@shakespeare.example/intibo24'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<identity
category='conference'
name='Shakespearean Chat Service'
type='text'/>
<feature var='urn:xmpp:mix:0'/>
<feature var='http://jabber.org/protocol/muc'/>
<x xmlns='jabber:x:data' type='result'>
<field var='FORM_TYPE' type='hidden'>
<value>urn:xmpp:mix:0#serviceinfo</value>
</field>
</x>
</query>
</iq>
]]></example>
<p>For the partially integrated service, it will be useful for clients that support both MIX and MUC to be able to determine that the server supports both protocols. For a MIX client, it will be useful to know the MUC service, so that this information can be shared with a MUC client invitation. This information is provided by the initial service discovery:</p>
<example caption="MIX Service responds with Disco Info result sharig MUC service location" ><![CDATA[
<iq from='mix.shakespeare.example'
id='lx09df27'
to='hag66@shakespeare.example/intibo24'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<identity
category='conference'
name='Shakespearean Chat Service'
type='text'/>
<feature var='urn:xmpp:mix:0'/>
<x xmlns='jabber:x:data' type='result'>
<field var='FORM_TYPE' type='hidden'>
<value>urn:xmpp:mix:0#serviceinfo</value>
</field>
<field var='muc-mirror'
type='jid-single'
label='Location of MUC mirror service'>
<value>chat.shakespeare.example</value>
</field>
</x>
</query>
</iq>
]]></example>
<p>The result is returned in an extended disco results in a form whose type value is 'urn:xmpp:mix:0#serviceinfo'. The field with var='muc-mirror' is the value of which is the mirrored MUC domain's JID. </p>
<p>Where a client supporting both MIX and MUC is given a reference to a MUC room, it is desirable that the client can determine the MIX channel and join using MIX. This is achieved by an equivalent extension to MUC service discover.</p>
<example caption="MUC Service responds with Disco Info result sharig MIX service location" ><![CDATA[
<iq from='chat.shakespeare.example'
id='lx09df27'
to='hag66@shakespeare.example/intibo24'
type='result'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<identity
category='conference'
name='Shakespearean Chat Service'
type='text'/>
<feature var='http://jabber.org/protocol/muc'/>
<x xmlns='jabber:x:data' type='result'>
<field var='FORM_TYPE' type='hidden'>
<value>urn:xmpp:mix:0#serviceinfo</value>
</field>
<field var='mix-mirror'
type='jid-single'
label='Location of MUC mirror service'>
<value>mix.shakespeare.example</value>
</field>
</x>
</query>
</iq>
]]></example>
<p>The result is returned in an extended disco results in a form whose type value is 'urn:xmpp:mix:0#serviceinfo'. The field with var='mix-mirror' is the value of which is the mirrored MIX domain's JID. </p>
<section2 topic="Choosing Which Invite to Send" anchor="mix-muc-invite-choice">
<p>
Where a client supports MUC and MIX and has determined that for a channel that the server also supports a MUC room, the client has a choice as to which type of invite to send. This SHOULD be done by determining if the client support MIX using the mechanism specified in
<link url='#mix-client-discovery'>Discovering Client MIX Capability</link>. If the client supports MIX a MIX invite SHOULD be sent.
</p>
</section2>
</section1>
<!--<section1 topic='Implementation Notes' anchor='impl'>
<p>OPTIONAL.</p>
</section1>
<section1 topic='Accessibility Considerations' anchor='access'>
<p>OPTIONAL.</p>
</section1>-->
<section1 topic="Capabilities not provided in MIX" anchor="not-included-from45">
<p>This section lists a number of capabilities not specified in this version of MIX which were provided in &xep0045;. </p>
<section2 topic="Password Controlled Channels" anchor="password-control">
<p>
&xep0045; provides a mechanism to control access to MUC rooms using passwords. An equivalent mechanism is not included in MIX, as it has a number of security issues. Control of access to channels is better achieved using an explicit list of participants.
</p>
</section2>
<section2 topic="Conversion from 1:1 Chat" anchor="chat-conversion">
<p>
&xep0045; describes how to convert from a 1:1 chat to a MUC room. Conversion from 1:1 chat is a straightforward and useful capability, that is not described in this version of the MIX specification. Options that may be considered in the future are:
</p>
<ol>
<li>Describe in a new separate XEP.</li>
<li>Describe in an updated version of this XEP.</li>
<li>Do not specify in a XEP and leave to implementer.</li>
</ol>
<p>QUESTION: Input on these choices is solicited. Dave Cridland votes for new XEP.</p>
</section2>
<section2 topic="Voice Control" anchor="voice-control">
<p>
&xep0045; defines a mechanism so that MUC moderators can control who is able to send messages to a MUC room using a "voice" mechanism. The current version of MIX does not include this.
</p>
<p>AUTHOR'S NOTE AND QUESTION: Input on the desirability of adding voice control to MIX is solicited. It would appear reasonably straightforward, and probably be achieved by adding two additional nodes to the MIX channel.</p>
</section2>
</section1>
<section1 topic='Internationalization Considerations' anchor='i18n'>
<p>TBD.</p>
<p>Discuss normalization of nicknames.</p>
</section1>
<section1 topic='Security Considerations' anchor='security'>
<p>TBD.</p>
<p>Topics to cover:</p>
<ul>
<li>transparent vs. opaque channels</li>
<li>nickname registration and security implications of normalization</li>
</ul>
</section1>
<section1 topic='IANA Considerations' anchor='iana'>
<p>None.</p>
</section1>
<section1 topic='XMPP Registrar Considerations' anchor='registrar'>
<p>Register a namespace.</p>
</section1>
<section1 topic='XML Schema' anchor='schema'>
<p>TBD.</p>
</section1>
<section1 topic='Acknowledgements' anchor='ack'>
<p>Thanks to the following who have made contributions: Dave Cridland, Philipp Hancke, Waqas Hussain, Georg Lukas, Ralph Meijer, Edwin Mons, Emmanuel Gil Peyrot, Florian Schmaus, Lance Stout, Sam Whited, Matthew Wild and one anonymous reviewer.</p>
</section1>
</xep>
<!--TODO: Query whole service for MAM. Provide data form for filtering by node ID.
TODO: Two config nodes - one public read one private read?
TODO: Open Issue: How many config nodes do you need? Do you do different access to different items within a node for reading? Writing?
TODO: Subscription option to check channel config (e.g., transparency of JIDs) before join.
-->
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