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Network Working GroupP. Saint-Andre
Internet-DraftJ. Miller
Expires: August 27, 2003Jabber Software Foundation
 February 26, 2003

XMPP Instant Messaging
draft-ietf-xmpp-im-04

Status of this Memo

This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.

Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."

The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt.

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This Internet-Draft will expire on August 27, 2003.

Copyright Notice

Copyright (C) The Internet Society (2003). All Rights Reserved.

Abstract

This document describes the specific extensions to and applications of the Extensible Messaging and Presence Protocol (XMPP) that are necessary to create a basic instant messaging and presence application such as that provided by the servers, clients, and other applications that comprise the XMPP-based Jabber network.



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Table of Contents




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1. Introduction

1.1 Overview

The core features of the Extensible Messaging and Presence Protocol are defined in XMPP Core[1]. These features -- specifically XML streams, stream authentication and encryption, and the <message/>, <presence/>, and <iq/> children of the stream root -- provide the building blocks for many types of near-real-time applications, which may be layered on top of the core by sending application-specific data scoped by particular XML namespaces. This document describes the extensions to and applications of XMPP Core that are used to create the basic functionality expected of an instant messaging and presence application as defined in RFC 2779[2]. Extended namespaces for many other functionality areas have been defined and continue to be defined by the Jabber Software Foundation[3], including service discovery, multi-user chat, data gathering and forms submission, feature negotiation, message composing events, message expiration, delayed delivery, file transfer, publish-subscribe, and transports for XML-RPC and SOAP; however, such functionality is not described herein because it is not required by RFC 2779[2].

1.2 Requirements

For the purposes of this document, we stipulate that a basic instant messaging and presence application needs to enable a user to perform the following high-level functionality by using a compliant client:

Detailed definitions of these functionality areas are contained in RFC 2779[2]; although XMPP IM meets those requirements, it was not designed explicitly with RFC 2779 in mind, since the base protocol evolved through an open development process within the Jabber open-source community, mainly in 1999.

1.3 Terminology

This document inherits the terminology defined in XMPP Core[1].

The capitalized key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119[4].

1.4 Discussion Venue

The authors welcome discussion and comments related to the topics presented in this document. The preferred forum is the <xmppwg@jabber.org> mailing list, for which archives and subscription information are available at <http://www.jabber.org/cgi-bin/mailman/listinfo/xmppwg/>.

1.5 Intellectual Property Notice

This document is in full compliance with all provisions of Section 10 of RFC 2026. Parts of this specification use the term "jabber" for identifying namespaces and other protocol syntax. Jabber[tm] is a registered trademark of Jabber, Inc. Jabber, Inc. grants permission to the IETF for use of the Jabber trademark in association with this specification and its successors, if any.



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2. Authentication and Authorization

In order to gain access to the network of XMPP-compliant applications and thus engage in standard IM functionality such as exchanging messages and presence, a user must first acquire an account on a server. Although account provisioning is outside the scope of XMPP, methods for doing so include account creation by a server administrator as well as in-band account registration using the 'jabber:iq:register' namespace; the latter method is defined by the Jabber Software Foundation[3] and appropriate documentation is available at the JSF's website.

In order to gain access to the network, a user MUST authenticate with the server hosting his or her account. If a user's client is capable of authenticating by means of SASL, it MUST include a 'version' attribute (set to a value of "1.0") within the opening <stream/> element with which it initiated communications with the server. The protocol describing how a client authenticates with a server using SASL is defined in XMPP Core[1].

Once a client has authenticated with a server using SASL, it MUST define a resource that the server can associate with the connection for purposes of authorization and addressing. This is necessary because stanzas sent to or received from the server within the context of an active session use a "full JID" (user@domain/resource) for addressing. Authorizing a resource is accomplished by means of the 'jabber:iq:auth' namespace as described below.

Step 1: Client queries server regarding information that is still required to begin a session:

<iq type="get" id="res_1">
  <query xmlns="jabber:iq:auth">
    <username>juliet</username>
  </query>
</iq>
      

Step 2: Server responds with the required fields (in this case, only the username and authorized resource):

<iq type="result" id="res_1">
  <query xmlns="jabber:iq:auth">
    <username>juliet</username>
    <resource/>
  </query>
</iq>
      

Step 3: Client sends name of authorized resource:

<iq type="set" id="res_2">
  <query xmlns="jabber:iq:auth">
    <username>juliet</username>
    <resource>balcony</resource>
  </query>
</iq>
      

Step 4: Server informs client of successful session initiation:

<iq type="result" id="res_2"/>
      

Step 4 (alt): Server informs client of error encountered during session initiation:

<iq type="result" id="res_2">
  <query xmlns="jabber:iq:auth">
    <username>juliet</username>
    <resource></resource>
  </query>
  <error code='406'>Not Acceptable (empty resource)</error>
</iq>
      

NOTE: Earlier iterations of the Jabber protocol contained a client-server authentication protocol that was enforced after the stream was negotiated; this protocol is not suppoted in XMPP but is documented by the Jabber Software Foundation[3] for historical purposes.



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3. Exchanging Messages

Exchanging messages is a basic use of XMPP and is effected when a user sends a message stanza to another user (or, more generally, another entity). As defined under Routing and Delivery Rules, the sender's server is responsible for delivering the message to the intended recipient (if the recipient is on the same server) or for routing the message to the recipient's server (if the recipient is on a different server).

Detailed information regarding the syntax of message stanzas and their defined attributes and child elements may be found in XMPP Core[1].

3.1 Specifying an Intended Recipient

A client SHOULD specify an intended recipient for the message by providing an appropriate JID in the 'to' attribute of the <message/> element. Normally, the value of the 'to' attribute specifies an entity other than the sending user. The intended recipient MAY be any valid JID (e.g., a user on the same server, a user on a different server, the server itself, another server, or a service). If the JID is invalid or cannot be contacted, the entity discovering that fact (usually the sender's or recipient's server) MUST return an error to the sender.

3.2 Specifying a Message Type

As mentioned in XMPP Core[1], there are several defined types of messages (specified by means of a 'type' attribute within the <message/> element). In the context of an instant messaging application, a client MAY include a message type in order to capture the conversational context of the message, thus providing a hint regarding presentation (e.g., in a GUI). If included, the 'type' attribute SHOULD have one of the following values (any other value MAY be ignored):

Although the 'type' attribute is OPTIONAL, it is considered polite to mirror the type in any replies to a message; furthermore, some specialized applications (e.g., a multi-user chat service) MAY at their discretion enforce the use of a particular message type (e.g., type='groupchat').

3.3 Specifying a Message Subject

A message stanza MAY contain a child <subject/> element specifying the subject of the message. The subject MUST NOT contain mixed content. Multiple <subject/> elements MAY be included, as long as each contains an 'xml:lang' attribute with a distinct value.

A message with a subject:

<message to="romeo@montague.net" from="juliet@capulet.com/balcony">
  <subject>Imploring</subject>
  <body>Wherefore art thou, Romeo?</body>
</message>
        

3.4 Specifying a Conversation Thread

A message stanza MAY contain a child <thread/> element specifying the conversation thread in which the message is situated, for the purpose of tracking the conversation. The content of the <thread/> element is a random string that is generated by the sender in accordance with the algorithm specified in XMPP Core[1]; this string SHOULD be copied back to the sender in subsequent replies.

A threaded conversation:

<message 
    to="romeo@montague.net/orchard" 
    from="juliet@capulet.com/balcony" 
    type="chat">
  <body>Art thou not Romeo, and a Montague?</body>
  <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
</message>

<message 
    to="juliet@capulet.com/balcony" 
    from="romeo@montague.net/orchard" 
    type="chat">
  <body>Neither, fair saint, if either thee dislike.</body>
  <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
</message>

<message 
    to="romeo@montague.net/orchard" 
    from="juliet@capulet.com/balcony" 
    type="chat">
  <body>How cam'st thou hither, tell me, and wherefore?</body>
  <thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
</message>
        

3.5 Specifying a Message Body

A message stanza MAY (and often will) contain a child <body/> element specifying the main content of the message as CDATA. The body MUST NOT contain mixed content. If it is necessary to provide the main message content in an alternate form (e.g., encrypted using the public key infrastructure or formatted using XHTML), the alternate form MUST be contained in an appropriately-namespaced child of the message stanza, as defined for any such extended namespace.

Multiple <body/> elements MAY be included, as long as each contains an 'xml:lang' attribute with a distinct value.

3.6 Specifying Additional Information

A message stanza MAY house an element containing content that extends the meaning of the message (e.g., an encrypted form of the message body). In common usage this child element is often the <x/> element but MAY be any element, as long as the 'xmlns' namespace declaration is something other than the streams namespace or the default namespace; this extended namespace defines all elements contained within the child element.

3.7 Message-Related Errors

If a message sent by a sender cannot be delivered, the entity discovering that fact (usually either the sender's or recipient's server) MUST return that message to the sender in a message stanza of type "error" along with an appropriate error message (for a list of error messages, see XMPP Core[1]).

A message-related error:

<message 
    to="juliet@capulet.com" 
    from="romeo@montague.net">
  <body>Sleep dwell upon thine eyes.</body>
</message>

<message
    to="romeo@montague.net"
    from="juliet@capulet.com" 
    type="error">
  <body>Sleep dwell upon thine eyes.</body>
  <error code="404">We're sorry, Juliet just died</error>
</message>
        

An entity that receives a message stanza of type 'error' MUST NOT respond to the stanza by sending a further message stanza of type 'error'; this helps to prevent looping.



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4. Exchanging Presence Information

Exchanging presence information is made relatively straightforward within XMPP by using presence stanzas. However, we see here a contrast to the handling of messages: although a client MAY send directed presence information to another entity, in general presence information is sent from a client to a server (with no 'to' address) and then broadcasted by the server to any entities that are subscribed to the presence of the sending entity. (Note: in the terminology of RFC 2778[5], the only watchers in XMPP are subscribers.)

Detailed information regarding the syntax of presence stanzas and their defined attributes and child elements may be found in XMPP Core[1].

4.1 Client and Server Responsibilities

When a client connects to a server, it SHOULD send an initial presence stanza to the server to express default availability. This presence stanza MUST possess no 'to' address (signalling that it is meant to be handled by the server on behalf of the user) and SHOULD have no type.

Upon receiving initial presence from a client, the server sends presence probes from the full JID (user@domain/resource) of the user to any remote entities that are subscribed to the user's presence (as represented in the user's roster) in order to determine if they are available. (The remote server is responsible for responding to the presence probe only when (1) the probing entity has been allowed to access the probed entity's presence, e.g., by server rules or user subscriptions, and (2) the probed entity is available; the probing entity's server then informs the probing entity of the probed entity's last known available presence, for all of the probed entity's resources if applicable.)

Throughout the active session of a connected resource, the server is responsible for broadcasting any changes in the availability status of the connected resource to the subscribed entities that are available, so that such entities are kept apprised of availability changes.

Finally, the server MUST notify all of the subscribed and available entities when a connected resource becomes unavailable.

4.2 Sending Initial Presence

Upon authenticating, a client SHOULD send initial presence to its server indicating that the connected resource is available for communications. This presence stanza MUST have no 'to' address and SHOULD have no type.

Initial presence sent from client to server:

<presence/>
        

4.3 Specifying Availability Status

A client MAY provide further information about its availability status by using the <show/> element. As defined in XMPP Core[1], the recognized values for the show element are "away", "chat", "xa", and "dnd".

Availability status:

<presence>
  <show>away</show>
</presence>
        

4.4 Specifying Detailed Status Information

In conjunction with the <show/> element, a client MAY provide detailed status information by using the <status/> element. The content of this element is a natural-language description of the client's current availability status.

Detailed status information:

<presence>
  <show>dnd</show>
  <status>Busy fighting the Romans</status>
</presence>
        

4.5 Probing for Presence

A server MAY probe for the current presence of another entity. A user or client SHOULD NOT send presence stanzas of type 'probe'.

4.6 Sending Final Presence

Upon ending its session with a server, a client SHOULD gracefully become unavailable by sending a final presence stanza that is explicitly of type unavailable.

Sending final presence to express unavailable state:

<presence type="unavailable"/>
        

Optionally, final presence MAY contain one or more <status/> elements specifying the reason why the user is no longer available.

The server MUST NOT depend on receiving final presence from a connected resource, since the resource may become unavailable unexpectedly. If a server detects that a resource has become unavailable for any reason (either gracefully or ungracefully), it MUST send <presence type="unavailable"/> to all online entities that are subscribed to the associated user's presence, as well as to any entities to which the user sent directed presence during the active session for that connected resource.

4.7 Determining When a Contact Went Offline

The server MUST maintain a record of the time at which a user became unavailable (whether gracefully or ungracefully). An authorized subscriber to that user's presence MAY determine the time of last activity by sending an IQ stanza to the user's bare JID (user@domain) containing an empty <query/> element scoped by the 'jabber:iq:last' namespace:

Requesting the last active time of a user:

<iq type='get' to='user@domain'>
  <query xmlns='jabber:iq:last'/>
</iq>
        

If the entity requesting the time of last activity is an authorized subscriber to the user's presence, the server MUST return an IQ stanza of type 'result' with the number of seconds since the user was last active:

Returning the last active time of a user:

<iq from='user@domain' type='result' to='subscriber@domain/resource'>
  <query seconds='76490' xmlns='jabber:iq:last'/>
</iq>
        

If the entity requesting the time of last activity is not an authorized subscriber to the user's presence, the server MUST return an IQ stanza of type 'error' with an error code of 403 (Forbidden):

Requester is forbidden to view the last active time of a user:

<iq from='user@domain' type='result' to='subscriber@domain/resource'>
  <query xmlns='jabber:iq:last'/>
  <error code='403'>Forbidden</error>
</iq>
        


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5. Managing Subscriptions

In order to protect the privacy of instant messaging users and any other entities, presence and availability information is made available only to other entities that the user has approved. When a user has agreed that another entity may view its presence, the entity is said to have a subscription to the user's presence information. Note well that a subscription lasts across sessions; indeed, it lasts until the subscriber unsubscribes or the subscribee cancels the previously-granted subscription. Subscriptions are completed within XMPP by sending presence stanzas containing specially-defined attributes.

Note that there are important interactions between subscriptions and rosters; these are defined under Integration of Roster Items and Presence Subscriptions.

5.1 Requesting a Subscription

A request to subscribe to another entity's presence is made by sending a presence stanza of type "subscribe".

Sending a subscription request:

<presence to="juliet@capulet.com" type="subscribe"/>
        

5.2 Handling a Subscription Request

When a client receives a subscription request from another entity, it MAY accept the request by sending a presence stanza of type "subscribed" or decline the request by sending a presence stanza of type "unsubscribed".

Accepting a subscription request:

<presence to="romeo@montague.net" type="subscribed"/>
        

Denying a presence subscription request:

<presence to="romeo@montague.net" type="unsubscribed"/>
        

A user's server MUST NOT automatically accept subscription requests on the user's behalf. All subscription requests MUST be directed to the user's client. If there is no connected resource associated with the user when the subscription request is received, the user's server MUST store the subscription request offline for delivery when the user next becomes available.

5.3 Cancelling a Subscription from Another Entity

If a user would like to cancel a previously-granted subscription request, it sends a presence stanza of type "unsubscribed".

Cancelling a previously granted subscription request:

<presence to="romeo@montague.net" type="unsubscribed"/>
        

5.4 Unsubscribing from Another Entity's Presence

If a user would like to unsubscribe from the presence of another entity, it sends a presence stanza of type "unsubscribe".

Unsubscribing from an entity's presence:

<presence to="juliet@capulet.com" type="unsubscribe"/>
        


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6. Managing One's Roster

In XMPP, one's contact list is called a roster. A roster is stored by the server on the user's behalf so that a user may access roster information from any connected resource.

Note that there are important interactions between rosters and subscriptions; these are defined under Integration of Roster Items and Presence Subscriptions.

6.1 Retrieving One's Roster on Login

Upon connecting to the server, a client MAY request the roster (however, because receiving the roster may not be desirable for all resources, e.g., a connection with limited bandwidth, the client's request for the roster is OPTIONAL). Note that if a connected resource does not request the roster during a session, it SHOULD never receive presence subscriptions and associated roster pushes.

Client requests current roster from server:

<iq type="get" id="roster_1">
  <query xmlns="jabber:iq:roster"/>
</iq>
        

Client receives roster from the server:

<iq 
    from="capulet.com"
    to="juliet@capulet.com/balcony"
    id="roster_1" 
    type="result">
  <query xmlns="jabber:iq:roster>
    <item 
        jid="romeo@montague.net" 
        name="Romeo" 
        subscription="both"/>
    <item 
        jid="mercutio@montague.net" 
        name="Mercutio" 
        subscription="both">
      <group>Friends</group>
    </item> 
    <item 
        jid="benvolio@montague.net" 
        name="Benvolio" 
        subscription="both">
      <group>Friends</group>
    </item> 
  </query>
</iq>
        

6.2 Adding a Roster Item

At any time, a user MAY add an item to his or her roster.

Client adds a new item:

<iq type="set" id="roster_2">
  <query xmlns="jabber:iq:roster">  
    <item 
        name="Nurse" 
        jid="nurse@capulet.com">
      <group>Servants</group>
    </item>
  </query>
</iq>
        

The server is responsible for updating the roster information in persistent storage, and also for pushing that change out to all connected resources associated with the user using an IQ stanza of type "set" (this is referred to as a "roster push"). This "roster push" enables all connected resources to remain in sync with the server-based roster information.

Server replies with an IQ result to the sending resource and pushes the updated roster information to all connected resources:

<iq 
    from="capulet.com" 
    to="juliet@capulet.com/balcony"
    type="result" 
    id="roster_2"/> 
<iq 
    from="capulet.com"
    to="juliet@capulet.com/balcony"
    type="set"/>
  <query xmlns="jabber:iq:roster">  
    <item 
        name="Nurse" 
        jid="nurse@capulet.com"
        subscription="none">
      <group>Servants</group>
    </item>
  </query>
</iq>
<iq 
    from="capulet.com"
    to="juliet@capulet.com/chamber"
    type="set"/>
  <query xmlns="jabber:iq:roster">  
    <item 
        name="Nurse" 
        jid="nurse@capulet.com"
        subscription="none">
      <group>Servants</group>
    </item>
  </query>
</iq>
        

Updating an existing roster item (e.g., changing the Group) is done in the same way as adding a new roster item, i.e., by sending the roster item in an IQ set to the server.

6.3 Deleting a Roster Item

At any time, a user MAY delete an item from its roster by doing an IQ set and making sure that the value of the 'subscription' attribute is "remove" (a compliant server MUST ignore any other values of the 'subscription' attribute when received from a client).

Client removes an item:

<iq type="set" id="roster_2">
  <query xmlns="jabber:iq:roster">  
    <item 
        name="Nurse" 
        jid="nurse@capulet.com"
        subscription="remove">
      <group>Servants</group>
    </item>
  </query>
</iq>
        

As with adding a roster item, when deleting a roster item the server is responsible for updating the roster information in persistent storage, and also for initiating a "roster push" to all connected resources associated with the user.

For further information about the implications of this command, see Removing a Roster Item and Cancelling All Subscriptions.



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7. Integration of Roster Items and Presence Subscriptions

7.1 Overview

Some level of integration between roster items and presence subscriptions is normally expected by instant messaging users. This section describes the level of integration that must be supported within XMPP IM.

There are four primary subscription states:

Each of these states is reflected in the roster of both the user and the contact, thus resulting in durable subscription states. The details regarding how these subscription states interact with roster items is explained in the following sub-sections.

As noted above, if a connected resource does not request the roster during a session, it SHOULD never receive presence subscriptions and the associated roster pushes.

7.2 User Subscribes to Contact

The process by which a user subscribes to a contact, including the interaction between roster items and subscription states, is defined below.

  1. In preparation for being able to render the contact in the user's client interface and for the server to keep track of the subscription, the user's client MUST send an IQ stanza of type='set' in the 'jabber:iq:roster' namespace for the new roster item; the <item/> element MUST possess a 'jid' attribute, MAY possess a 'name' attribute, may contain a <group/> child, and MUST NOT posses a 'subscription' attribute:
    <iq type='set' id='int1'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='contact@domain'
            name='MyContact'/>
      </query>
    </iq>
              
  2. The server then MUST (1) reply with an IQ stanza of type='result' and (2) initiate a "roster push" for the new roster item to all connected resources associated with this user, setting the subscription state set to 'none':
    <iq
        type='result'
        to='user@domain/resource'
        id='int1'/>
    
    <iq type='set' to='user@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='contact@domain'
            name='MyContact'
            subscription='none'/>
      </query>
    </iq>
              
  3. In order to initiate the subscription, the user's client MUST then send a presence stanza of type='subscribe' to the contact:
    <presence to='contact@domain' type='subscribe'/>
              
  4. The server MUST then initiate a second "roster push" to all connected resources associated with the user, setting the contact to the pending sub-state of the 'none' subscription state; this pending sub-state is denoted by the inclusion of the ask='subscribe' attribute in the roster item:
    <iq type='set' to='user@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='contact@domain'
            name='MyContact'
            subscription='none'
            ask='subscribe'/>
      </query>
    </iq>
              
  5. The server MUST also deliver the presence stanza to the contact or route it to the contact's server for delivery to the contact, first stamping the stanza with the user's bare JID as the 'from' address:
    <presence
        to='contact@domain'
        from='user@domain'
        type='subscribe'/>
              
  6. If the contact is online (i.e., there is a connected resource associated with the contact's account), the contact must now decide whether or not to accept the subscription request. (If the contact is offline, the contact's server MUST store the subscription request offline for delivery when the contact next becomes available.) Here we will assume the "happy path" that the contact accepts the subscription, in which case the contact's client MAY send a roster set to the server specifying the desired nickname and group for the user, and MUST send a presence stanza of type='subscribed' to the user.
    <iq type='set'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='user@domain'
            name='SomeUser'/>
      </query>
    </iq>
    
    <presence to='user@domain' type='subscribed'/>
              
  7. The contact's server MUST now initiate a "roster push" to all connected resources associated with the contact, containing a roster item for the user with the subscription state set to 'from':
    <iq type='set' to='contact@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='user@domain'
            name='SomeUser'
            subscription='from'/>
      </query>
    </iq>
              
  8. As a result of the fact that the contact has accepted the subscription request, the user's server MUST (1) deliver the presence stanza of type='subscribed' from the contact to the user, and (2) initiate a "roster push" to all connected resources associated with the user, containing an updated roster item for the contact with the subscription type set to a value of "to":
    <presence
        to='user@domain'
        type='subscribed'
        from='contact@domain'/>
    
    <iq type='set' to='user@domain/resource'>
      <query xmlns='jabber:iq:roster'>
      <item
          jid='contact@domain'
          name='MyContact'
          subscription='to'/>
      </query>
    </iq>
              

From the perspective of the user, there is now a subscription to the contact; from the perspective of the contact, there is now a subscription from the user. The contact's server MUST now send the contact's current presence information to the user. (Note: If at this point the user sends another subscription request to the contact, the user's server MUST "swallow" that request and not send it on the contact.)

7.2.1 Alternate Flow

The above activity flow represents the "happy path" related to the user's subscription request to the contact. The main alternate flow occurs if the contact denies the user's subscription request; in order to deny the request, the contact's client MUST send a presence stanza of type "unsubscribed" to the user:

<presence to='user@domain' type='unsubscribed'/>
          

The user's server MUST then (1) deliver that presence stanza to the user and (2) initiate a "roster push" to all connected resources associated with the user, with the subscription attribute set to a value of "none":

<presence
    to='user@domain'
    type='unsubscribed'
    from='contact@domain'/>

<iq type='set' to='user@domain/resource'>
  <query xmlns='jabber:iq:roster'>
    <item
        jid='contact@domain'
        name='MyContact'
        subscription='none'/>
  </query>
</iq>
          

As a result of this activity, the contact is now in the user's roster with a subscription state of "none", whereas the user is not in the contact's roster at all.

7.3 Creating a Mutual Subscription

The user and contaact can build on the foregoing to create a mutual subscription (i.e., a subscription of type "both"). The process is defined below.

  1. The contact MUST send a subscription request to the user (subject to user preferences, the contact's client MAY send this automatically):
    <presence to='user@domain' type='subscribe'/>
              
  2. The contact's server MUST then initiate a "roster push" to all connected resources associated with the contact, with the user still in the 'from' subscription state but with a pending 'to' subscription denoted by the inclusion of the ask='subscribe' attribute in the roster item:
    <iq type='set' to='contact@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='user@domain'
            name='SomeUser'
            subscription='from'
            ask='subscribe'/>
      </query>
    </iq>
              
  3. If the user is online (i.e., there is a connected resource associated with the user's account), the user must now decide whether or not to accept the subscription request. (If the user is offline, the user's server MUST store the subscription request offline for delivery when the user next becomes available.) Here we will assume the "happy path" that the user accepts the subscription, in which case the user's client MUST send a presence stanza of type='subscribed' to the contact.
    <presence to='contact@domain' type='subscribed'/>
              
  4. The user's server MUST then initiate a "roster push" to all connected resources associated with the user, containing a roster item for the contact with the subscription attribute set to a value of "both":
    <iq type='set' to='user@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='contact@domain'
            name='MyContact'
            subscription='both'/>
      </query>
    </iq>
              
  5. As a result of the fact that the user has accepted the subscription request, the contact's server MUST (1) deliver the presence stanza of type='subscribed' from the user to the contact, and (2) initiate a "roster push" to all connected resources associated with the contact, containing an updated roster item for the user with the subscription type set to a value of "both":
    <presence
        to='contact@domain'
        from='user@domain'
        type='subscribed'/>
    
    <iq type='set' to='contact@domain/resource'>
      <query xmlns='jabber:iq:roster'>
      <item
          jid='user@domain'
          name='SomeUser'
          subscription='both'/>
      </query>
    </iq>
              

The user and the contact now have a mutual subscription to each other's presence -- i.e., the subscription is of type 'both'. The user's server MUST now send the user's current presence information to the contact. (Note: If at this point the user sends a subscription request to the contact or the contact sends a subscription request to the user, the sending user's server will "swallow" that request and not send it on the intended recipient.)

7.3.1 Alternate Flow

The above activity flow represents the "happy path" related to the contact's subscription request to the user. The main alternate flow occurs if the user denies the contacts's subscription request; in order to deny the request, the user's client MUST send a presence stanza of type "unsubscribed" to the contact:

<presence to='contact@domain' type='unsubscribed'/>
          

The contact's server MUST then (1) deliver that presence stanza to the contact and (2) initiate a "roster push" to all connected resources associated with the contact, with the subscription attribute set to a value of "from" and with no 'ask' attribute:

<presence
    to='contact@domain'
    from='user@domain'
    type='unsubscribed'/>

<iq type='set' to='contact@domain/resource'>
  <query xmlns='jabber:iq:roster'>
    <item
        jid='user@domain'
        name='SomeUser'
        subscription='from'/>
  </query>
</iq>
          

As a result of this activity, there has been no change in the subscription state; i.e., the contact is in the user's roster with a subscription state of "to" and the user is in the contact's roster with a subscription state of "from".

7.4 Unsubscribing

At any time after subscribing to a contact's presence, a user MAY unsubscribe. While the XML that the user sends to make this happen is the same in all instances, the subsequent subscription state is different depending on the subscription state obtaining when the unsubscribe command is sent. Both possible scenarios are defined below.

7.4.1 Case #1: Subscription Type 'to'

In the first case, the user has a subscription to the contact but the contact does not have a subscription to the user (i.e., the subscription is not yet mutual).

  1. In order to unsubscribe from the contact's presence, the user MUST send a presence stanza of type "unsubscribe" to the contact:
    <presence to='contact@domain' type='unsubscribe'/>
                
  2. As a result, the user's server MUST send a "roster push" to each connected resource associated with the user, containing a roster item for the contact with the 'ask' attribute set to unsubscribe to indicate that the unsubscribe is pending:
    <iq type='set' to='user@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='contact@domain'
            name='MyContact'
            subscription='to'
            ask='unsubscribe'/>
      </query>
    </iq>
                
  3. Since the unsubscribe command does not need to be approved by the contact, the contact's server then SHOULD auto-reply on behalf of the contact by sending a presence stanza of type "unsubscribed" to the user:
    <presence
        to='user@domain'
        from='contact@domain'
        type='unsubscribed'/>
                
  4. The contact's server also MUST initiate a "roster push" to all connected resources associated with the contact, containing a roster item for the user with the 'subscription' attribute set to a value of "none" (if the contact is offline, the contact's server MUST modify the roster item and send that modified item the next time the contact requests the roster):
    <iq type='set' to='contact@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='user@domain'
            name='SomeUser'
            subscription='none'/>
      </query>
    </iq>
                
  5. As a result of the fact that the contact has acknowledged the unsubscribe command, the user's server MUST (1) deliver the presence stanza of type='unsubscribed' from the contact to the user, and (2) initiate a "roster push" to all connected resources associated with the user, containing an updated roster item for the contact with the subscription type set to a value of "none" and with no 'ask' attribute:
    <presence
        to='user@domain'
        from='contact@domain'
        type='unsubscribed'/>
    
    <iq type='set'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='contact@domain'
            subscription='none'
            name='MyContact'/>
      </query>
    </iq>
                

7.4.2 Case #2: Subscription Type 'both'

In the second case, the user has a subscription to the contact and the contact also has a subscription to the user.

  1. In order to unsubscribe from the contact's presence, the user MUST send a presence stanza of type "unsubscribe" to the contact:
    <presence to='contact@domain' type='unsubscribe'/>
                
  2. As a result, the user's server MUST send a "roster push" to each connected resource associated with the user, containing a roster item for the contact with the 'ask' attribute set to unsubscribe to indicate that the unsubscribe is pending:
    <iq type='set' to='user@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='contact@domain'
            name='MyContact'
            subscription='both'
            ask='unsubscribe'/>
      </query>
    </iq>
                
  3. Since the unsubscribe command does not need to be approved by the contact, the contact's server then SHOULD auto-reply on behalf of the contact by sending a presence stanza of type "unsubscribed" to the user:
    <presence
        to='user@domain'
        from='contact@domain'
        type='unsubscribed'/>
                
  4. The contact's server also MUST initiate a "roster push" to all connected resources associated with the contact, containing a roster item for the user with the 'subscription' attribute set to a value of "to" (if the contact is offline, the contact's server MUST modify the roster item and send that modified item the next time the contact requests the roster):
    <iq type='set' to='contact@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='user@domain'
            name='SomeUser'
            subscription='to'/>
      </query>
    </iq>
                
  5. As a result of the fact that the contact has acknowledged the unsubscribe command, the user's server MUST (1) deliver the presence stanza of type='unsubscribed' from the contact to the user, and (2) initiate a "roster push" to all connected resources associated with the user, containing an updated roster item for the contact with the subscription type set to a value of "from" and with no 'ask' attribute:
    <iq type='set'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='contact@domain'
            subscription='none'
            name='MyContact'/>
      </query>
    </iq>
                

NOTE: Obviously this does not result in removal of the roster item from the user's roster, and the contact still has a subscription to the user's presence. In order to more completely cancel a mutual subscription and fully remove the roster item from the user's roster, the user should update the roster item with subscription='remove' as defined in Removing a Roster Item and Cancelling All Subscriptions.

7.5 Cancelling a Subscription

At any time after approving a subscription request from a user, a contact MAY cancel that subscription. While the XML that the contact sends to make this happen is the same in all instances, the subsequent subscription state is different depending on the subscription state obtaining when the cancellation is sent. Both possible scenarios are defined below.

7.5.1 Case #1: Subscription Type 'from'

In the first case, the user has a subscription to the contact but the contact does not have a subscription to the user (i.e., the subscription is not yet mutual).

  1. In order to cancel the user's subscription, the contact MUST send a presence stanza of type "unsubscribed" to the user:
    <presence to='user@domain' type='unsubscribed'/>
                
  2. As a result, the contact's server MUST send a "roster push" to each connected resource associated with the contact, containing a roster item for the user with the 'subscription' attribute set to a value of "none":
    <iq type='set' to='contact@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='user@domain'
            name='SomeUser'
            subscription='none'/>
      </query>
    </iq>
                
  3. The user's server MUST then initiate a "roster push" to all connected resources associated with the user, containing a roster item for the contact with the 'subscription' attribute set to a value of "none" (if the user is offline, the user's server MUST modify the roster item and send that modified item the next time the user requests the roster):
    <iq type='set' to='user@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='contact@domain'
            name='MyContact'
            subscription='none'/>
      </query>
    </iq>
                

7.5.2 Case #2: Subscription Type 'both'

In the second case, the user has a subscription to the contact and the contact also has a subscription to the user.

  1. In order to cancel the user's subscription, the user MUST send a presence stanza of type "unsubscribed" to the user:
    <presence to='user@domain' type='unsubscribed'/>
                
  2. As a result, the contact's server MUST send a "roster push" to each connected resource associated with the contact, containing a roster item for the user with the 'subscription' attribute set to a value of "to":
    <iq type='set' to='contact@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='user@domain'
            name='SomeUser'
            subscription='to'/>
      </query>
    </iq>
                
  3. The user's server MUST then initiate a "roster push" to all connected resources associated with the user, containing a roster item for the contact with the 'subscription' attribute set to a value of "from" (if the user is offline, the user's server MUST modify the roster item and send that modified item the next time the user requests the roster):
    <iq type='set' to='user@domain/resource'>
      <query xmlns='jabber:iq:roster'>
        <item
            jid='contact@domain'
            name='MyContact'
            subscription='from'/>
      </query>
    </iq>
                

NOTE: Obviously this does not result in removal of the roster item from the contact's roster, and the contact still has a subscription to the user's presence. In order to more completely cancel a mutual subscription and fully remove the roster item from the contact's roster, the contact should update the roster item with subscription='remove' as defined in Removing a Roster Item and Cancelling All Subscriptions.

7.6 Removing a Roster Item and Cancelling All Subscriptions

Because there may be many steps involved in completely removing a roster item and reverting the subscription state to "none", XMPP IM includes a "shortcut" method for doing so. The process may be initiated by either a contact or a user no matter what the current subscription state is, by means of sending a roster set with the subscription attribute set to a value of "remove".

For example, a user may send the following XML:

<iq type='set'>
  <query xmlns='jabber:iq:roster'>
    <item
        jid='contact@domain'
        name='MyContact'
        subscription='remove'/>
  </query>
</iq>
        

When the user removes a contact from his or her roster by setting the 'subscription' attribute to a value of "remove", the user's server MUST automatically cancel any existing presence subscription between the user and the contact by sending presence stanzas of type "unsubscribe" and "unsubscribed" from the user to the contact.

A contact may also send such a command, resulting in the same type of system behavior.



 TOC 

8. Blocking Communication

Most instant messaging systems have found it necessary to implement some method for users to block communications from particular other users (this is also required by sections 5.1.5, 5.1.15, 5.3.2, and 5.4.10 of RFC 2779[2]). In XMPP this is done using the 'jabber:iq:privacy' namespace by managing one's privacy lists.

Server-side privacy lists enable successful completion of the following use cases:

Note well that presence notifications do not include presence subscriptions, only presence information that is broadcasted to entities that are subscribed to a user's presence information. Thus this includes presence stanzas with no 'type' attribute or of "type='unavailable'" only.

8.1 Syntax

A user may define one or more privacy lists, which are stored by the user's server. Each <list/> element contains one or more rule in the form of <item/> elements, and each <item/> element uses attributes to define a privacy rule type, a specific value within the type, the relevant action, and the place of the item in the processing order.

The syntax is as follows:

<iq>
  <query xmlns='jabber:iq:privacy'>
    <list name='foo'>
      <item
          type='[jid|group|subscription]'
          value='bar'
          action='[accept|deny]'
          order='nonNegativeInteger'/>
    </list>
  </query>
</iq>
        

If the type is "jid", then the 'value' attribute MUST contain a valid Jabber ID. JIDs are matched in the following order: "user@domain/resource", then "user@domain", then "domain". If the value is "user@domain", then any connected resource for that user@domain matches. If the value is "domain", then any user@domain matches.

If the type is "group", then the 'value' attribute MUST contain the name of a group in the user's roster.

If the type is "subscription", then the 'value' attribute MUST be one of "both", "to", "from", or "none" as defined in XMPP Core[1].

If no 'type' attribute is included, the rule provides the "fall-through" case.

The 'action' attribute MUST be included and its value MUST be either "accept" or "deny".

The 'order' attribute MUST be included and its value MUST be a non-negative integer that is unique among all items in the list. (If a client attempts to create or update a list with non-unique order values, the server MUST return a 400 "Bad Request" error to the client.)

8.2 Processing Order

The order in which privacy list items are processed by the server is important. List items MUST be processed in ascending order determined by the values of the 'order' attribute for each <item/>.

As soon as a stanza is matched against a privacy list, the server can appropriately handle the stanza and cease processing.

If no fall-through item is provided in a list, the fall-through action is assumed to be "accept".

8.3 Retrieving One's Privacy Lists

Client requests names of privacy lists from server:

<iq type='get' id='getlist1'>
  <query xmlns='jabber:iq:privacy'/>
</iq>
        

Server sends names of privacy lists to client, including default list and active list:

<iq type='result' id='getlist1' to='romeo@montague.net/orchard'>
  <query xmlns='jabber:iq:privacy'>
    <default name='public'/>
    <active name='private'/>
    <list name='public'>
    <list name='private'/>
    <list name='special'/>
  </query>
</iq>
        

Client requests complete privacy lists from server:

<iq type='get' id='getlist2'>
  <query xmlns='jabber:iq:privacy'>
    <list name='public'>
    <list name='private'/>
    <list name='special'/>
  </query>
</iq>
        

Server sends complete privacy lists to client:

<iq type='result' id='getlist2' to='romeo@montague.net/orchard'>
  <query xmlns='jabber:iq:privacy'>
    <list name='public'>
      <item jid='tybalt@capulet.com' type='deny' order='1'/>
      <item action='allow' order='2'/>
    </list>
    <list name='private'>
      <item type='subscription' value='both' action='allow' order='10'/>
      <item action='deny' order='15'/>
    </list>
    <list name='special'>
      <item type='jid' value='juliet@capulet.com' action='allow' order='6'/>
      <item type='jid' value='benvolio@shakespeare.lit' action='allow' order='7'/>
      <item type='jid' value='mercutio@shakespeare.lit' action='allow' order='42'/>
      <item action='deny'/>
    </list>
  </query>
</iq>
        

In this example, the user has three lists: (1) 'public', which allows communications from everyone except one specific entity; (2) 'private', which allows communications only from contacts who have a bi-directional subscription with the user; and (3) 'special', which allows communications only from three specific entities. The active list currently being applied by the server is the 'private' list.

8.4 Managing Active Lists

In order to set or change the active list currently being applied by the server, the user MUST send an IQ stanza of type 'set' with a <query/> element scoped by the 'jabber:iq:privacy' namespace that contains an empty <active/> child element possessing a 'name' attribute whose value is set to the desired list name.

Client requests change of active list:

<iq type='set' id='active1'>
  <query xmlns='jabber:iq:privacy'>
    <active name='special'/>
  </query>
</iq>
        

The server MUST activate and apply the requested list before sending the result is sent back to the client.

Server acknowledges success of active list change:

<iq type='result' id='active1' to='juliet@capulet.com/balcony'/>
        

In order to decline the use of any active list (i.e., to use the domain's stanza routing rules), a user MUST send an empty <active/> element with no name.

Client declines the use of active lists:

<iq type='set' id='active2'>
  <query xmlns='jabber:iq:privacy'>
    <active/>
  </query>
</iq>
        

8.5 Managing the Default List

In order to change the default list associated with an account, the user MUST send an IQ stanza of type 'set' with a <query/> element scoped by the 'jabber:iq:privacy' namespace that contains an empty <default/> child element possessing a 'name' attribute whose value is set to the desired list name.

Client requests change of default list:

<iq type='set' id='default1'>
  <query xmlns='jabber:iq:privacy'>
    <default name='special'/>
  </query>
</iq>
        

Server acknowledges success of default list change:

<iq type='result' id='default1' to='juliet@capulet.com/balcony'/>
        

In order to decline the use of the default list (i.e., to use the domain's stanza routing rules), a user MUST send an empty <default/> element with no name.

Client declines the use of the default list:

<iq type='set' id='default2'>
  <query xmlns='jabber:iq:privacy'>
    <default/>
  </query>
</iq>
        

8.6 Editing a Privacy List

In order to edit a privacy list, the user MUST send an IQ stanza of type 'set' with a <query/> element scoped by the 'jabber:iq:privacy' namespace that contains one or more <list/> child elements possessing a 'name' attribute whose value is set to the list name the user would like to edit. Each <list/> element MUST contain one or more <item/> elements, which specify the user's desired changes to the list by including all elements in the list (not the "delta"); the same protocol is used to create a new list.

Client edits a privacy list:

<iq type='set' id='edit1'>
  <query xmlns='jabber:iq:privacy'>
    <list name='public'>
      <item type='jid' value='tybalt@capulet.com' action='deny' order='3'/>
      <item type='jid' value='paris@shakespeare.lit' action='deny' order='5'/>
      <item action='allow' order='68'/>
    </list>
  </query>
</iq>
        

Server acknowledges success of list edit:

<iq type='result' id='edit1' to='juliet@capulet.com/balcony'/>
        

In this example, the user has added one additional entity to the "blacklist" portion of this privacy list.

8.7 Removing a Privacy List

In order to remove a privacy list, the user MUST send an IQ stanza of type 'set' with a <query/> element scoped by the 'jabber:iq:privacy' namespace that contains one or more empty <list/> child elements possessing a 'name' attribute whose value is set to the list name the user would like to remove.

Client removes a privacy list:

<iq type='set' id='remove1'>
  <query xmlns='jabber:iq:privacy'>
    <list name='private'/>
  </query>
</iq>
        

Server acknowledges success of list removal:

<iq type='result' id='remove1' to='juliet@capulet.com/balcony'/>
        

If a user attempts to remove an active list or the default list, the server MUST return a 405 (Not Allowed) error to the user.

8.8 Blocking Messages

Server-side privacy lists enable a user to block incoming messages from other users based on the other user's JID, roster group, or subscription status, or globally. The following examples illustrate the required protocol.

User blocks based on JID:

<iq type='set' id='msg1'>
  <query xmlns='jabber:iq:privacy'>
    <list name='message-jid-example'>
      <item type='jid' value='tybalt@capulet.com' type='deny' order='3'>
        <message/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive messages from the user with the specified JID.

User blocks based on roster group:

<iq type='set' id='msg2'>
  <query xmlns='jabber:iq:privacy'>
    <list name='message-group-example'>
      <item type='group' value='Enemies' type='deny' order='4'>
        <message/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive messages from any users in the specified roster group.

User blocks based on subscription type:

<iq type='set' id='msg2'>
  <query xmlns='jabber:iq:privacy'>
    <list name='message-sub-example'>
      <item type='subscription' value='none' type='deny' order='5'>
        <message/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive messages from any users with the specified subscription type.

User blocks globally:

<iq type='set' id='msg4'>
  <query xmlns='jabber:iq:privacy'>
    <list name='message-global-example'>
      <item type='deny' order='6'>
        <message/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive messages from any other users.

8.9 Blocking Inbound Presence Notifications

Server-side privacy lists enable a user to block incoming presence notifications from other users based on the other user's JID, roster group, or subscription status, or globally. The following examples illustrate the required protocol.

User blocks based on JID:

<iq type='set' id='presin1'>
  <query xmlns='jabber:iq:privacy'>
    <list name='presin-jid-example'>
      <item type='jid' value='tybalt@capulet.com' type='deny' order='7'>
        <presence-in/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive presence notifications from the user with the specified JID.

User blocks based on roster group:

<iq type='set' id='presin2'>
  <query xmlns='jabber:iq:privacy'>
    <list name='presin-group-example'>
      <item type='group' value='Enemies' type='deny' order='8'>
        <presence-in/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive presence notifications from any users in the specified roster group.

User blocks based on subscription type:

<iq type='set' id='presin3'>
  <query xmlns='jabber:iq:privacy'>
    <list name='presin-sub-example'>
      <item type='subscription' value='none' type='deny' order='9'>
        <presence-in/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive presence notifications from any users with the specified subscription type.

User blocks globally:

<iq type='set' id='presin4'>
  <query xmlns='jabber:iq:privacy'>
    <list name='presin-global-example'>
      <item type='deny' order='11'>
        <presence-in/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive presence notifications from any other users.

8.10 Blocking Outbound Presence Notifications

Server-side privacy lists enable a user to block outgoing presence notifications to other users based on the other user's JID, roster group, or subscription status, or globally. The following examples illustrate the required protocol.

User blocks based on JID:

<iq type='set' id='presout1'>
  <query xmlns='jabber:iq:privacy'>
    <list name='presout-jid-example'>
      <item type='jid' value='tybalt@capulet.com' type='deny' order='13'>
        <presence-out/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not send presence notifications to the user with the specified JID.

User blocks based on roster group:

<iq type='set' id='presout2'>
  <query xmlns='jabber:iq:privacy'>
    <list name='presout-group-example'>
      <item type='group' value='Enemies' type='deny' order='15'>
        <presence-out/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not send presence notifications to any users in the specified roster group.

User blocks based on subscription type:

<iq type='set' id='presout3'>
  <query xmlns='jabber:iq:privacy'>
    <list name='presout-sub-example'>
      <item type='subscription' value='none' type='deny' order='17'>
        <presence-out/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not send presence notifications to any users with the specified subscription type.

User blocks globally:

<iq type='set' id='presout4'>
  <query xmlns='jabber:iq:privacy'>
    <list name='presout-global-example'>
      <item type='deny' order='23'>
        <presence-out/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not send presence notifications to any other users.

8.11 Blocking IQs

Server-side privacy lists enable a user to block incoming IQ requests from other users based on the other user's JID, roster group, or subscription status, or globally. The following examples illustrate the required protocol.

User blocks based on JID:

<iq type='set' id='msg1'>
  <query xmlns='jabber:iq:privacy'>
    <list name='iq-jid-example'>
      <item type='jid' value='tybalt@capulet.com' type='deny' order='29'>
        <iq/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive IQ requests from the user with the specified JID.

User blocks based on roster group:

<iq type='set' id='msg2'>
  <query xmlns='jabber:iq:privacy'>
    <list name='iq-group-example'>
      <item type='group' value='Enemies' type='deny' order='31'>
        <iq/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive IQ requests from any users in the specified roster group.

User blocks based on subscription type:

<iq type='set' id='msg2'>
  <query xmlns='jabber:iq:privacy'>
    <list name='iq-sub-example'>
      <item type='subscription' value='none' type='deny' order='17'>
        <iq/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive IQ requests from any users with the specified subscription type.

User blocks globally:

<iq type='set' id='msg4'>
  <query xmlns='jabber:iq:privacy'>
    <list name='iq-global-example'>
      <item type='deny' order='1'>
        <iq/>
      </item>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive IQ requests from any other users.

8.12 Blocking All Communication

Server-side privacy lists enable a user to block all communications from and presence to other users based on the other user's JID, roster group, or subscription status, or globally. The following examples illustrate the required protocol.

User blocks based on JID:

<iq type='set' id='all1'>
  <query xmlns='jabber:iq:privacy'>
    <list name='all-jid-example'>
      <item type='jid' value='tybalt@capulet.com' type='deny' order='23'>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive any communications from, nor send presence to, the user with the specified JID.

User blocks based on roster group:

<iq type='set' id='all2'>
  <query xmlns='jabber:iq:privacy'>
    <list name='all-group-example'>
      <item type='group' value='Enemies' type='deny' order='13'/>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive any communications from, nor send presence to, any users in the specified roster group.

User blocks based on subscription type:

<iq type='set' id='all3'>
  <query xmlns='jabber:iq:privacy'>
    <list name='all-sub-example'>
      <item type='subscription' value='none' type='deny' order='11'/>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive any communications from, nor send presence to, any users with the specified subscription type.

User blocks globally:

<iq type='set' id='all4'>
  <query xmlns='jabber:iq:privacy'>
    <list name='all-global-example'>
      <item type='deny' order='7'/>
    </list>
  </query>
</iq>
        

As a result of creating and applying the foregoing list, the user will not receive any communications from, nor send presence to, any other users.

8.13 Blocked Entity Attempts to Communicate with User

If a blocked entity attempts to send messages or presence notifications to the user, the user's server SHOULD silently drop the stanza and MUST NOT return an error to the sending entity.

If a blocked entity attempts to send an IQ stanza of type "get" or "set" to the user, the user's server MUST return a 501 (Not Implemented) error to the sending entity, since this is the standard error code sent from a client that does not understand the namespace of an IQ get or set. IQ stanzas of other types SHOULD be silently dropped by the server.

Blocked entity attempts to send IQ get:

<iq 
    type='get' 
    to='romeo@montague.net' 
    from='tybalt@capulet.com/pda' 
    id='probing1'>
  <query xmlns='jabber:iq:version'/>
</iq>
        

Server returns error to blocked entity:

<iq 
    type='error'
    from='romeo@montague.net' 
    to='tybalt@capulet.com/pda'
    id='probing1'>
  <query xmlns='jabber:iq:version'/>
  <error code='501'>Not Implemented</error>
</message>
        

8.14 Higher-Level Heuristics

When building a representation of a higher-level privacy heuristic, a client SHOULD use the simplest possible representation. For example, the heuristic "block all communications with any user not in my roster" could be constructed in any of the following ways:

The final representation is the simplest and SHOULD be used; here is the XML that would be sent in this case:

Client constructs simple representation of heuristic for accepting communications only with those in the user's roster:

<iq type='set' id='heuristic1'>
  <query xmlns='jabber:iq:privacy'>
    <list name='heuristic-example'>
      <item type='subscription' value='none' type='deny' order='437'/>
    </list>
  </query>
</iq>
        

A more complete list of such heuristics and their simplest representations may be provided in a future revision of this document.



 TOC 

9. Routing and Delivery Rules

9.1 Client Generation of To Addresses

Many XMPP stanzas possess a 'to' address that specifies the intended recipient of the stanza. When a server receives a stanza possessing a 'to' attribute from a connected client, it is responsible for either directly delivering the stanza to the intended recipient (if the recipient is served by the same server) or for routing the stanza to another server (if the recipient is not served by the same server). (This does not necessary imply that the recipient is on a different domain from the sender, since one server could host multiple domains.) If delivery to the intended recipient is unsuccessful or the recipient's server cannot be contacted, the sender's server is responsible for returning an error to the sender; if the recipient's server can be contacted but delivery by the recipient's server to the recipient is unsuccessful, the recipient's server is responsible for returning an error to the sender by way of the sender's server.

If a client does not specify a 'to' address on a stanza, it is implied that the stanza is meant to be handled by the sender's server on behalf of the sender. Although this functionality is normally not used in the case of message stanzas, it is quite common with regard to both presence and IQ stanzas. In the case of presence stanzas, the user's presence information is normally sent from the client to the user's server without a 'to' attribute, and subsequently broadcasted to all entities that are subscribed to the sender's presence information using a classic publish-subscribe model. In the case of IQ stanzas, requests in many extended namespaces (e.g., jabber:iq:roster) are normally sent from the client to the server without a 'to' attribute, and handled by the server on behalf of the user (e.g., to manage roster information stored by the server).

If a user's client would like to request information about the user's server itself (e.g., for the purpose of service discovery), it MUST include the server's JID in the 'to' address of the IQ request.

9.2 Server Handling of XML Stanzas

XML stanzas that are not handled directly by a server (e.g., for the purpose of data storage or rebroadcasting) are routed or delivered to the intended recipient of the stanza as represented by a JID in the 'to' attribute. The following rules apply:



 TOC 

10. IANA Considerations

For IANA considerations, refer to the relevant section of XMPP Core[1].



 TOC 

11. Security Considerations

For security considerations, refer to the relevant section of XMPP Core[1].



 TOC 

References

[1] Saint-Andre, P. and J. Miller, "XMPP Core (draft-ietf-xmpp-core-04, work in progress)", February 2003.
[2] Day, M., Aggarwal, S., Mohr, G. and J. Vincent, "A Model for Presence and Instant Messaging", RFC 2779, February 2000.
[3] Jabber Software Foundation, "Jabber Software Foundation", August 2001.
[4] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[5] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and Instant Messaging", RFC 2778, February 2000.
[6] Dawson, F. and T. Howes, "vCard MIME Directory Profile", RFC 2426, September 1998.


 TOC 

Authors' Addresses

  Peter Saint-Andre
  Jabber Software Foundation
EMail:  stpeter@jabber.org
URI:  http://www.jabber.org/people/stpeter.php
  
  Jeremie Miller
  Jabber Software Foundation
EMail:  jeremie@jabber.org
URI:  http://www.jabber.org/people/jer.php


 TOC 

Appendix A. vCards

This section is provided for informational purposes only and is not normative.

Sections 3.1.3 and 4.1.4 of RFC 2779[2] require that it be possible to retrieve non-IM contact information for other users (e.g., telephone number or email address). An XML representation of the vCard specification defined in RFC 2426[6] is in common use within the Jabber community to provide such information. For the sake of completeness, this section describes that protocol. This section is non-normative.

The basic functionality is for a user to store and retrieve an XML representation of his or her vCard using the data storage capabilities native to all existing Jabber server implementations. This is done by sending an <iq/> of type "set" (storage) or "get" (retrieval) to one's Jabber server containing a <vCard/> child scoped by the 'vcard-temp' namespace, with the <vCard/> element containing the actual vCard-XML elements as defined by the vCard-XML DTD. Other users may then view one's vCard information. (There is currently no access control over who may view vCard information.)

A.1 Retrieving One's vCard

A user may retrieve his or her own vCard by sending XML of the following form to his or her own JID:

<iq to='stpeter@jabber.org' type='get' id='vcard1'>
  <vCard xmlns='vcard-temp'/>
</iq>
          

The server MUST then return the vCard to the user:

<iq 
    from='stpeter@jabber.org'
    to='stpeter@jabber.org/Gabber'
    type='result'
    id='v1'>
  <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.jabber.org/people/stpeter.php</URL>
    <BDAY>1966-08-06</BDAY>
    <ORG>
      <ORGNAME>Jabber Software Foundation</ORGNAME>
      <ORGUNIT/>
    </ORG>
    <TITLE>Executive Director</TITLE>
    <ROLE>Patron Saint</ROLE>
    <TEL><VOICE/><WORK/><NUMBER>303-308-3282</NUMBER></TEL>
    <TEL><FAX/><WORK/><NUMBER/></TEL>
    <TEL><MSG/><WORK/><NUMBER/></TEL>
    <ADR>
      <WORK/>
      <EXTADD>Suite 600</EXTADD>
      <STREET>1899 Wynkoop Street</STREET>
      <LOCALITY>Denver</LOCALITY>
      <REGION>CO</REGION>
      <PCODE>80202</PCODE>
      <CTRY>USA</CTRY>
    </ADR>
    <TEL><VOICE/><HOME/><NUMBER>303-555-1212</NUMBER></TEL>
    <TEL><FAX/><HOME/><NUMBER/></TEL>
    <TEL><MSG/><HOME/><NUMBER/></TEL>
    <ADR>
      <HOME/>
      <EXTADD/>
      <STREET/>
      <LOCALITY>Denver</LOCALITY>
      <REGION>CO</REGION>
      <PCODE>80209</PCODE>
      <CTRY>USA</CTRY>
    </ADR>
    <EMAIL><INTERNET/><PREF/><USERID>stpeter@jabber.org</USERID></EMAIL>
    <JABBERID>stpeter@jabber.org</JABBERID>
    <DESC>
      More information about me is located on my 
      personal website: http://www.saint-andre.com/
    </DESC>
  </vCard>
</iq>
          

A.2 Updating One's vCard

A user may update his or her vCard by sending an IQ of type "set" to the server, following the format in the previous use case.

If a user attempts to perform an IQ set on another user's vCard, the server must return a 403 "Forbidden" error.

A.3 Viewing Another User's vCard

A user may view another user's vCard by sending an IQ of type "get" to the other user's bare JID. A compliant server must return the vCard to the requestor and not forward the IQ to the requestee's connected resource.

<iq 
    to='jer@jabber.org'
    type='get'
    id='v3'>
  <vCard xmlns='vcard-temp'/>
</iq>
          

The server should then return the other user's vCard to the requestor:

<iq 
    from='jer@jabber.org' 
    to='stpeter@jabber.org/home' 
    type='result'
    id='v3'>
  <vCard xmlns='vcard-temp'>
    <FN>JeremieMiller</FN>
    <N>
      <GIVEN>Jeremie</GIVEN>
      <FAMILY>Miller</FAMILY>
      <MIDDLE/>
    </N>
    <NICKNAME>jer</NICKNAME>
    <EMAIL><INTERNET/><PREF/><USERID>jeremie@jabber.org</USERID></EMAIL>
    <JABBERID>jer@jabber.org</JABBERID>
  </vCard>
</iq>
          


 TOC 

Appendix B. Formal Definitions

B.1 Schema for jabber:iq:last

<?xml version='1.0' encoding='UTF-8'?>
<xsd:schema
    xmlns:xsd='http://www.w3.org/2001/XMLSchema'
    targetNamespace='http://www.jabber.org/protocol'
    xmlns='http://www.jabber.org/protocol'
    elementFormDefault='qualified'>

  <xsd:element name='query'>
    <xsd:complexType>
      <xsd:attribute name='seconds' type='xsd:unsignedLong' use='optional'/>
    </xsd:complexType>
  </xsd:element>

</xsd:schema>
          

B.2 Schema for jabber:iq:privacy

<?xml version='1.0' encoding='UTF-8'?>
<xsd:schema
    xmlns:xsd='http://www.w3.org/2001/XMLSchema'
    targetNamespace='http://www.jabber.org/protocol'
    xmlns='http://www.jabber.org/protocol'
    elementFormDefault='qualified'>

  <xsd:element name='query'>
    <xsd:complexType>
      <xsd:choice minOccurs='0' maxOccurs='unbounded'>
        <xsd:element ref='active' minOccurs='0' maxOccurs='1'/>
        <xsd:element ref='default' minOccurs='0' maxOccurs='1'/>
        <xsd:element ref='list' minOccurs='0' maxOccurs='unbounded'/>
      </xsd:choice>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name='active'>
    <xsd:complexType>
      <xsd:attribute name='name' type='xsd:string' use='required'/>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name='default'>
    <xsd:complexType>
      <xsd:attribute name='name' type='xsd:string' use='required'/>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name='list'>
    <xsd:complexType>
      <xsd:choice minOccurs='0' maxOccurs='unbounded'>
        <xsd:element ref='item' minOccurs='0' maxOccurs='unbounded'/>
      </xsd:choice>
      <xsd:attribute name='name' type='xsd:string' use='required'/>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name='item'>
    <xsd:complexType>
      <xsd:choice> 
        <xsd:element ref='iq' minOccurs='0' maxOccurs='1'/>
        <xsd:element ref='message' minOccurs='0' maxOccurs='1'/>
        <xsd:element ref='presence-in' minOccurs='0' maxOccurs='1'/>
        <xsd:element ref='presence-out' minOccurs='0' maxOccurs='1'/>
      </xsd:choice>
      <xsd:attribute name='action' use='required'>
        <xsd:simpleType>
          <xsd:restriction base='xsd:NCName'>
            <xsd:enumeration value='allow'/>
            <xsd:enumeration value='deny'/>
          </xsd:restriction>
        </xsd:simpleType>
      </xsd:attribute>
      <xsd:attribute name='order' type='xsd:nonNegativeInteger' use='required'/>
      <xsd:attribute name='type' use='optional'>
        <xsd:simpleType>
          <xsd:restriction base='xsd:NCName'>
            <xsd:enumeration value='group'/>
            <xsd:enumeration value='jid'/>
            <xsd:enumeration value='subscription'/>
          </xsd:restriction>
        </xsd:simpleType>
      </xsd:attribute>
      <xsd:attribute name='value' type='xsd:string' use='optional'/>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name='iq'/>
  <xsd:element name='message'/>
  <xsd:element name='presence'/>

</xsd:schema>
          

B.3 Schema for jabber:iq:roster

<?xml version='1.0' encoding='UTF-8'?>
<xsd:schema
    xmlns:xsd='http://www.w3.org/2001/XMLSchema'
    targetNamespace='http://www.jabber.org/protocol'
    xmlns='http://www.jabber.org/protocol'
    elementFormDefault='qualified'>

  <xsd:element name='query'>
    <xsd:complexType>
      <xsd:sequence minOccurs='0' maxOccurs='unbounded'>
        <xsd:element ref='item'/>
      </xsd:sequence>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name='item'>
    <xsd:complexType>
      <xsd:sequence minOccurs='0' maxOccurs='unbounded'>
        <xsd:element ref='group'/>
      </xsd:sequence>
      <xsd:attribute name='jid' type='xsd:string' use='required'/>
      <xsd:attribute name='name' type='xsd:string' use='optional'/>
      <xsd:attribute name='subscription' use='optional'>
        <xsd:simpleType>
          <xsd:restriction base='xsd:string'>
            <xsd:enumeration value='to'/>
            <xsd:enumeration value='from'/>
            <xsd:enumeration value='both'/>
            <xsd:enumeration value='none'/>
            <xsd:enumeration value='remove'/>
          </xsd:restriction>
        </xsd:simpleType>
      </xsd:attribute>
      <xsd:attribute name='ask' use='optional'>
        <xsd:simpleType>
          <xsd:restriction base='xsd:string'>
            <xsd:enumeration value='subscribe'/>
            <xsd:enumeration value='unsubscribe'/>
          </xsd:restriction>
        </xsd:simpleType>
      </xsd:attribute>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name='group' type='xsd:string'/>

</xsd:schema>
          

B.4 DTD for vcard-temp

The following DTD is a slightly modified version of that contained in the second vCard-XML Internet-Draft authored by Frank Dawson. The only modifications were to add the JABBERID and DESC elements.

<?xml version="1.0" encoding="UTF-8"?>

<!--
Copyright (C) The Internet Society (2000). All Rights Reserved.

This document and translations of it may be copied and
furnished to others, and derivative works that comment
on or otherwise explain it or assist in its implmentation 
may be prepared, copied, published and distributed, in whole
or in part, without restriction of any kind, provided that
the above copyright notice and this paragraph are included
on all such copies and derivative works.

However, this document itself may not be modified in any
way, such as by removing the copyright notice or references
to the Internet Society or other Internet organizations,
except as needed for the purpose of developing Internet
standards in which case the procedures for copyrights
defined in the Internet Standards process MUST be followed,
or as required to translate it into languages other than English.

The limited permissions granted above are perpetual and will
not be revoked by the Internet Society or its successors or
assigns.

This document and the information contained herein is provided
on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE
USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR
ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
PARTICULAR PURPOSE.
-->

<!-- ==== -->

<!-- Root element and container for one
  or more vCard objects -->
<!ELEMENT xCard (vCard)+>

<!-- Individual vCard container -->
<!ELEMENT vCard (
  (VERSION, FN, N),
  (NICKNAME?,
  PHOTO?, 
  BDAY?, 
  ADR?, 
  LABEL?, 
  TEL?, 
  EMAIL?,
  JABBERID?,
  MAILER?, 
  TZ?, 
  GEO?, 
  TITLE?, 
  ROLE?,  
  LOGO?, 
  AGENT?, 
  ORG?, 
  CATEGORIES?, 
  NOTE?, 
  PRODID?, 
  REV?, 
  SORT-STRING?, 
  SOUND?, 
  UID?, 
  URL?, 
  CLASS?, 
  KEY?,
  DESC?
)*)>

  <!-- vCard specification version property. 
    This MUST be 2.0, if the document conforms to RFC 2426. -->
  <!ELEMENT VERSION (#PCDATA)>

  <!-- Formatted or display name property. -->
  <!ELEMENT FN (#PCDATA)>

  <!-- Structured name property. Name components with multiple
    values must be specified as a comma separated
	list of values. -->
  <!ELEMENT N ( FAMILY?, GIVEN?, MIDDLE?, PREFIX?, SUFFIX?)>
  
    <!ELEMENT FAMILY (#PCDATA)>
    <!ELEMENT GIVEN (#PCDATA)>
    <!ELEMENT MIDDLE (#PCDATA)>
    <!ELEMENT PREFIX (#PCDATA)>
    <!ELEMENT SUFFIX (#PCDATA)>

  <!-- Nickname property. Multiple nicknames must be
    specified as a comma separated list value. -->
  <!ELEMENT NICKNAME (#PCDATA)>

  <!-- Photograph property. Value is either a BASE64 encoded
    binary value or a URI to the external content. -->
  <!ELEMENT PHOTO ((TYPE, BINVAL) | EXTVAL)>

  <!-- Birthday property. Value must be an ISO 8601 formatted
    date or date/time value. -->
  <!ELEMENT BDAY (#PCDATA)>

  <!-- Structured address property. Address components with
    multiple values must be specified as a comma separated list
    of values. -->
  <!ELEMENT ADR (
    HOME?, 
    WORK?, 
    POSTAL?, 
    PARCEL?, 
    (DOM | INTL)?, 
    PREF?, 
    POBOX?, 
    EXTADR?, 
    STREET?, 
    LOCALITY?, 
    REGION?, 
    PCODE?, 
    CTRY?
  )>
  
    <!ELEMENT POBOX (#PCDATA)>
    <!ELEMENT EXTADR (#PCDATA)>
    <!ELEMENT STREET (#PCDATA)>
    <!ELEMENT LOCALITY (#PCDATA)>
    <!ELEMENT REGION (#PCDATA)>
    <!ELEMENT PCODE (#PCDATA)>
    <!ELEMENT CTRY (#PCDATA)>

  <!-- Address label property. -->
  <!ELEMENT LABEL (
    HOME?, 
    WORK?, 
    POSTAL?, 
    PARCEL?, 
    (DOM | INTL)?, 
    PREF?, 
    LINE+
  )>

    <!-- Individual label lines. -->
    <!ELEMENT LINE (#PCDATA)>

  <!-- Telephone number property. -->
  <!ELEMENT TEL (
    HOME?, 
    WORK?, 
    VOICE?, 
    FAX?, 
    PAGER?, 
    MSG?, 
    CELL?, 
    VIDEO?, 
    BBS?, 
    MODEM?, 
    ISDN?, 
    PCS?, 
    PREF?, 
    NUMBER
  )>

    <!-- Phone number value. -->
    <!ELEMENT NUMBER (#PCDATA)>

  <!-- Email address property. Default type is INTERNET. -->
  <!ELEMENT EMAIL (
    HOME?, 
    WORK?, 
    INTERNET?, 
    X400?, 
    USERID
  )>

    <!ELEMENT USERID (#PCDATA)>
  
  <!-- Jabber ID. Value must be in the form of user@domain. -->
  <!ELEMENT JABBERID (#PCDATA)>
  
  <!-- Mailer (e.g., Mail User Agent Type) property. -->
  <!ELEMENT MAILER (#PCDATA)>
  
  <!-- Time zone's Standard Time UTC offset. Value must be an
    ISO 8601 formatted UTC offset. -->
  <!ELEMENT TZ (#PCDATA)>
  
  <!-- Geographical position. Values are the decimal degress of
    LATitude and LONgitude. The value should be specified to 
    six decimal places.-->
  <!ELEMENT GEO (LAT, LON)>
  
    <!-- Latitude value. -->
    <!ELEMENT LAT (#PCDATA)>
	
    <!-- Longitude value. -->
    <!ELEMENT LON (#PCDATA)>
	
  <!-- Title property. -->
  <!ELEMENT TITLE (#PCDATA)>

  <!-- Role property. -->
  <!ELEMENT ROLE (#PCDATA)>
  
  <!-- Organization logo property. -->
  <!ELEMENT LOGO ((TYPE, BINVAL) | EXTVAL)>
  
  <!-- Administrative agent property. -->
  <!ELEMENT AGENT (vCard | EXTVAL)>
  
  <!-- Organizational name and units property. -->
  <!ELEMENT ORG (ORGNAME, ORGUNIT*)>
  
    <!ELEMENT ORGNAME (#PCDATA)>
  
    <!ELEMENT ORGUNIT (#PCDATA)>
  
  <!-- Application specific categories property. -->
  <!ELEMENT CATEGORIES (KEYWORD+)>
  
    <!ELEMENT KEYWORD (#PCDATA)>
  
  <!-- Commentary note property. -->
  <!ELEMENT NOTE (#PCDATA)>
  
  <!-- Identifier of product that generated the vCard property. -->
  <!ELEMENT PRODID (#PCDATA)>
  
  <!-- Last revised property. The value must be an 
       ISO 8601 formatted UTC date/time. -->
  <!ELEMENT REV (#PCDATA)>
  
  <!-- Sort string property. -->
  <!ELEMENT SORT-STRING (#PCDATA)>
  
  <!-- Formatted name pronunciation property. The value is 
       either a textual phonetic pronunciation, a BASE64 
       encoded binary digital audio pronunciation or a URI to
       an external binary digital audio pronunciation.-->	
  <!ELEMENT SOUND (PHONETIC | BINVAL | EXTVAL)>
  
    <!-- Textual phonetic pronunciation. -->
    <!ELEMENT PHONETIC (#PCDATA)>
   
  <!-- Unique identifier property. -->
  <!ELEMENT UID (#PCDATA)>
  
  <!-- Directory URL property. -->
  <!ELEMENT URL (#PCDATA)>

  <!-- Description. -->
  <!ELEMENT DESC (#PCDATA)>
  
  <!-- Privacy classification property. -->
  <!ELEMENT CLASS (PUBLIC | PRIVATE | CONFIDENTIAL)>
  
    <!ELEMENT PUBLIC EMPTY>
	
    <!ELEMENT PRIVATE EMPTY>
	
    <!ELEMENT CONFIDENTIAL EMPTY>
	
  <!-- Authentication credential or encryption  key property. -->
  <!ELEMENT KEY (TYPE?, CRED)>
  
    <!ELEMENT CRED (#PCDATA)>

<!-- ==== -->

<!-- Common elements. -->

<!-- Addressing type indicators. -->
<!ELEMENT HOME EMPTY>
<!ELEMENT WORK EMPTY>
<!ELEMENT POSTAL EMPTY>
<!ELEMENT PARCEL EMPTY>
<!ELEMENT DOM EMPTY>
<!ELEMENT INTL EMPTY>
<!ELEMENT PREF EMPTY>
<!ELEMENT VOICE EMPTY>
<!ELEMENT FAX EMPTY>
<!ELEMENT PAGER EMPTY>
<!ELEMENT MSG EMPTY>
<!ELEMENT CELL EMPTY>
<!ELEMENT VIDEO EMPTY>
<!ELEMENT BBS EMPTY>
<!ELEMENT MODEM EMPTY>
<!ELEMENT ISDN EMPTY>
<!ELEMENT PCS EMPTY>
<!ELEMENT INTERNET EMPTY>
<!ELEMENT X400 EMPTY>

<!-- Format type parameter. -->
<!ELEMENT TYPE (#PCDATA)>

<!-- Base64 encoded binary value. -->
<!ELEMENT BINVAL (#PCDATA)>

<!-- URI to external binary value -->
<!ELEMENT EXTVAL (#PCDATA)>

<!-- ==== -->
          


 TOC 

Appendix C. Revision History

Note to RFC editor: please remove this entire appendix, and the corresponding entries in the table of contents, prior to publication.

C.1 Changes from draft-ietf-xmpp-im-03

C.2 Changes from draft-ietf-xmpp-im-02

C.3 Changes from draft-ietf-xmpp-im-01

C.4 Changes from draft-ietf-xmpp-im-00

C.5 Changes from draft-miller-xmpp-im-02



 TOC 

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Acknowledgement