Network Working Group P. Saint-Andre
Internet-Draft J. Miller
Expires: August 24, 2003 Jabber Software Foundation
February 23, 2003
XMPP Instant Messaging
draft-ietf-xmpp-im-03
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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This Internet-Draft will expire on August 24, 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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2 Requirements . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4 Discussion Venue . . . . . . . . . . . . . . . . . . . . . . 5
1.5 Intellectual Property Notice . . . . . . . . . . . . . . . . 5
2. Authentication and Authorization . . . . . . . . . . . . . . 6
3. Exchanging Messages . . . . . . . . . . . . . . . . . . . . 7
3.1 Specifying an Intended Recipient . . . . . . . . . . . . . . 7
3.2 Specifying a Message Type . . . . . . . . . . . . . . . . . 7
3.3 Specifying a Message Subject . . . . . . . . . . . . . . . . 8
3.4 Specifying a Conversation Thread . . . . . . . . . . . . . . 8
3.5 Specifying a Message Body . . . . . . . . . . . . . . . . . 9
3.6 Specifying Additional Information . . . . . . . . . . . . . 9
3.7 Message-Related Errors . . . . . . . . . . . . . . . . . . . 10
4. Exchanging Presence Information . . . . . . . . . . . . . . 11
4.1 Client and Server Responsibilities . . . . . . . . . . . . . 11
4.2 Sending Initial Presence . . . . . . . . . . . . . . . . . . 11
4.3 Specifying Availability Status . . . . . . . . . . . . . . . 12
4.4 Specifying Detailed Status Information . . . . . . . . . . . 12
4.5 Probing for Presence . . . . . . . . . . . . . . . . . . . . 12
4.6 Sending Final Presence . . . . . . . . . . . . . . . . . . . 12
4.7 Determining When a Contact Went Offline . . . . . . . . . . 13
5. Managing Subscriptions . . . . . . . . . . . . . . . . . . . 14
5.1 Requesting a Subscription . . . . . . . . . . . . . . . . . 14
5.2 Handling a Subscription Request . . . . . . . . . . . . . . 14
5.3 Cancelling a Subscription from Another Entity . . . . . . . 14
5.4 Unsubscribing from Another Entity's Presence . . . . . . . . 15
6. Managing One's Roster . . . . . . . . . . . . . . . . . . . 16
6.1 Retrieving One's Roster on Login . . . . . . . . . . . . . . 16
6.2 Adding a Roster Item . . . . . . . . . . . . . . . . . . . . 17
6.3 Deleting a Roster Item . . . . . . . . . . . . . . . . . . . 18
7. Integration of Roster Items and Presence Subscriptions . . . 20
7.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.2 User Subscribes to Contact . . . . . . . . . . . . . . . . . 20
7.3 Creating a Mutual Subscription . . . . . . . . . . . . . . . 24
7.4 Unsubscribing . . . . . . . . . . . . . . . . . . . . . . . 26
7.4.1 Case #1: Subscription Type 'to' . . . . . . . . . . . . . . 26
7.4.2 Case #2: Subscription Type 'both' . . . . . . . . . . . . . 28
7.5 Cancelling a Subscription . . . . . . . . . . . . . . . . . 29
7.5.1 Case #1: Subscription Type 'from' . . . . . . . . . . . . . 29
7.5.2 Case #2: Subscription Type 'both' . . . . . . . . . . . . . 30
7.6 Removing a Roster Item and Cancelling All Subscriptions . . 31
8. Blocking Communication . . . . . . . . . . . . . . . . . . . 33
8.1 Retrieving One's Privacy Lists . . . . . . . . . . . . . . . 33
8.2 Managing Active Lists . . . . . . . . . . . . . . . . . . . 35
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8.3 Managing the Default List . . . . . . . . . . . . . . . . . 35
8.4 Editing a Privacy List . . . . . . . . . . . . . . . . . . . 36
8.5 Removing a Privacy List . . . . . . . . . . . . . . . . . . 37
8.6 Blocking Messages . . . . . . . . . . . . . . . . . . . . . 37
8.7 Blocking Inbound Presence . . . . . . . . . . . . . . . . . 39
8.8 Blocking Outbound Presence . . . . . . . . . . . . . . . . . 40
8.9 Blocking IQs . . . . . . . . . . . . . . . . . . . . . . . . 42
8.10 Blocking All Communication . . . . . . . . . . . . . . . . . 43
8.11 Blocked Entity Attempts to Send Message to User . . . . . . 45
8.12 Higher-Level Heuristics . . . . . . . . . . . . . . . . . . 45
8.13 Processing Order . . . . . . . . . . . . . . . . . . . . . . 46
9. Security Considerations . . . . . . . . . . . . . . . . . . 48
References . . . . . . . . . . . . . . . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 49
A. vCards . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
A.1 Retrieving One's vCard . . . . . . . . . . . . . . . . . . . 50
A.2 Updating One's vCard . . . . . . . . . . . . . . . . . . . . 51
A.3 Viewing Another User's vCard . . . . . . . . . . . . . . . . 52
B. Formal Definitions . . . . . . . . . . . . . . . . . . . . . 53
B.1 Schema for jabber:iq:last . . . . . . . . . . . . . . . . . 53
B.2 Schema for jabber:iq:privacy . . . . . . . . . . . . . . . . 53
B.3 Schema for jabber:iq:roster . . . . . . . . . . . . . . . . 54
B.4 DTD for vcard-temp . . . . . . . . . . . . . . . . . . . . . 55
C. Revision History . . . . . . . . . . . . . . . . . . . . . . 63
C.1 Changes from draft-ietf-xmpp-im-02 . . . . . . . . . . . . . 63
C.2 Changes from draft-ietf-xmpp-im-01 . . . . . . . . . . . . . 63
C.3 Changes from draft-ietf-xmpp-im-00 . . . . . . . . . . . . . 63
C.4 Changes from draft-miller-xmpp-im-02 . . . . . . . . . . . . 63
Intellectual Property and Copyright Statements . . . . . . . 65
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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:
o Authenticate with a server
o Exchange messages with other users
o Exchange presence information with other users
o Manage subscriptions to and from other users
o Manage the items in the user's contact list (in XMPP this is
called a "roster")
o Block communications to or from specific other users
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 in 1999.
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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].
After authenticating, a user MUST also provide a resource name for
the current session, for the purpose of addressing; the protocol for
providing a resource is also defined in XMPP Core [1].
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 in the "Routing and Delivery Rules"
section of XMPP Core [1], 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).
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) SHOULD 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):
o chat -- The message is sent in the context of a one-to-one chat
conversation.
o groupchat -- The message is sent in the context of a multi-user
chat environment.
o headline -- The message is generated by an automated service that
delivers content (news, sports, market information, etc.).
o error - A message returned to a sender specifying an error
associated with a previous message sent by the sender (for a full
list of error messages, see XMPP Core [1])
Although the 'type' attribute is OPTIONAL, it is considered polite to
mirror the type in any replies to a message; furthermore, some
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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.
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>
Multiple <subject/> elements MAY be included, as long as each
contains an 'xml:lang' attribute with a distinct value.
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 thread. 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
MAY be copied back to the sender in subsequent replies. If included,
the <thread/> element MUST have no attributes and MUST NOT contain
mixed content.
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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
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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) SHOULD 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.)
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.
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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"/>
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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.
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.
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
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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.
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).
Client requests current roster from server:
<iq id="roster_1" type="get">
<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>
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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.
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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"
id="roster_3"/>
<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"
id="roster_3"/>
<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 SHOULD ignore any other values of the
'subscription' attribute when received from a client).
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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
Section 7.6.
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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:
o None -- Neither the user nor the contact is subscribed to the
other's presence
o To -- The user is subscribed to the contact's presence but there
is no subscription from the contact to the user
o From -- There is a subscription from the contact to the user, but
the user has not subscribed to the contact's presence
o Both -- Both the user and the contact are subscribed to each
other's presence
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.
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; 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>
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</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:
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<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":
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<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>
9. 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. (Note: If at this point the user
sends another subscription request to the contact, the user's
server will "swallow" that request and not send it on the
contact.)
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>
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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='subscribe'/>
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":
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<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'. (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.)
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
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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='from'/>
<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 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:
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<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:
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<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 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
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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 Section 7.6.
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'
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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 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 a
presence stanza of type "unsubscribed" to the user:
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<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 Section 7.6.
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".
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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.
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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 (also
called "zebra lists" since they are flexible combinations of
blacklists and whitelists).
Server-side privacy lists enable successful completion of the
following use cases:
o Retreiving one's privacy lists.
o Adding, removing, and editing one's privacy lists.
o Setting, changing, or declining active lists.
o Setting, changing, or declining the default list.
o Allowing or denying messages based on JID, group, or subscription
type (or globally).
o Allowing or denying inbound presence information based on JID,
group, or subscription type (or globally).
o Allowing or denying outbound presence information based on JID,
group, or subscription type (or globally).
o Allowing or denying IQs based on JID, group, or subscription type
(or globally).
o Allowing or denying all communications based on JID, group, or
subscription type (or globally).
8.1 Retrieving One's Privacy Lists
Client requests names of privacy lists from server:
<iq type='get' id='getlist1'>
<query xmlns='jabber:iq:privacy'/>
</iq>
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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'/>
<item action='allow'/>
</list>
<list name='private'>
<item filter='subscription' value='both' action='allow'/>
<item action='deny'/>
</list>
<list name='special'>
<item filter='jid' value='juliet@capulet.com' action='allow'/>
<item filter='jid' value='benvolio@shakespeare.lit' action='allow'/>
<item filter='jid' value='mercutio@shakespeare.lit' action='allow'/>
<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
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allows communications only from three specific entities. The active
list currently being applied by the server is the 'private' list.
8.2 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>
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>
8.3 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.
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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 any 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 active lists:
<iq type='set' id='default2'>
<query xmlns='jabber:iq:privacy'>
<default/>
</query>
</iq>
8.4 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 filter='jid' value='tybalt@capulet.com' action='deny'/>
<item filter='jid' value='paris@shakespeare.lit' action='deny'/>
<item action='allow'/>
</list>
</query>
</iq>
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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.
8.5 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'/>
8.6 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 filter='jid' value='tybalt@capulet.com' type='deny'>
<message/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
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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 filter='group' value='Enemies' type='deny'>
<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 filter='subscription' value='none' type='deny'>
<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'>
<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.
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8.7 Blocking Inbound Presence
Server-side privacy lists enable a user to block incoming presence
information 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 filter='jid' value='tybalt@capulet.com' type='deny'>
<presence-in/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive presence information 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 filter='group' value='Enemies' type='deny'>
<presence-in/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive presence information from any users in the specified
roster group.
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User blocks based on subscription type:
<iq type='set' id='presin3'>
<query xmlns='jabber:iq:privacy'>
<list name='presin-sub-example'>
<item filter='subscription' value='none' type='deny'>
<presence-in/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive presence information 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'>
<presence-in/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not receive presence information from any other users.
8.8 Blocking Outbound Presence
Server-side privacy lists enable a user to block outgoing presence
information to other users based on the other user's JID, roster
group, or subscription status, or globally. The following examples
illustrate the required protocol.
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User blocks based on JID:
<iq type='set' id='presout1'>
<query xmlns='jabber:iq:privacy'>
<list name='presout-jid-example'>
<item filter='jid' value='tybalt@capulet.com' type='deny'>
<presence-out/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not send presence information 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 filter='group' value='Enemies' type='deny'>
<presence-out/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not send presence information 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 filter='subscription' value='none' type='deny'>
<presence-out/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not send presence information to any users with the specified
subscription type.
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User blocks globally:
<iq type='set' id='presout4'>
<query xmlns='jabber:iq:privacy'>
<list name='presout-global-example'>
<item type='deny'>
<presence-out/>
</item>
</list>
</query>
</iq>
As a result of creating and applying the foregoing list, the user
will not send presence information to any other users.
8.9 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 filter='jid' value='tybalt@capulet.com' type='deny'>
<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 filter='group' value='Enemies' type='deny'>
<iq/>
</item>
</list>
</query>
</iq>
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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 filter='subscription' value='none' type='deny'>
<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'>
<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.
8.10 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.
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User blocks based on JID:
<iq type='set' id='all1'>
<query xmlns='jabber:iq:privacy'>
<list name='all-jid-example'>
<item filter='jid' value='tybalt@capulet.com' type='deny'>
</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 filter='group' value='Enemies' type='deny'/>
</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 filter='subscription' value='none' type='deny'/>
</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.
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User blocks globally:
<iq type='set' id='all4'>
<query xmlns='jabber:iq:privacy'>
<list name='all-global-example'>
<item type='deny'/>
</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.
8.11 Blocked Entity Attempts to Send Message to User
If a blocked entity attempts to send a message to the user, the
user's server SHOULD return an error of type 405 (Not Allowed) to the
sending entity.
Blocked entity attempts to send message:
<message to='romeo@montague.net' from='tybalt@capulet.com/pda'>
<body>Have at thee, coward!</body>
</message>
Server returns error to blacklisted entity:
<message
type='error'
from='romeo@montague.net'
to='tybalt@capulet.com/pda'>
<body>Have at thee, coward!</body>
<error code='405'>Not Allowed</error>
</message>
Such error messages SHOULD also be sent regarding IQ messages, not
regarding presence.
8.12 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:
o accept communications from all JIDs in my roster (i.e., listing
each JID as a separate list item), but deny communications with
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everyone else
o accept communications from any user who is in one of the groups
that make up my roster (i.e., listing each group as a separate
list item), but deny communications from everyone else
o accept communications from any user with whom I have a
subscription of 'both' or 'to' or 'from' (i.e., listing each
subscription value separately), but deny communications from
everyone else
o deny communications from anyone whose subscription state is 'none'
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 filter='subscription' value='none' type='deny'/>
</list>
</query>
</iq>
A more complete list of such heuristics and their simplest
representations may be provided in a future revision of this
document.
8.13 Processing Order
The order in which privacy list items are processed by the server is
important. List items MUST be processed in order of granularity,
according to the following hierarchy of 'filter' attribute values
(from most to least granular):
1. jid
2. group
3. subscription
4. No 'filter' attribute ("fall-through" case)
As soon as a rule is matched, the server can appropriately route the
stanza and cease processing.
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If no fall-through item is provided in a list, the fall-through
action is assumed to be "accept".
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9. Security Considerations
For security considerations, refer to the relevant section of XMPP
Core [1].
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References
[1] Saint-Andre, P. and J. Miller, "XMPP Core
(draft-ietf-xmpp-core-03, 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,
<http://www.ietf.org/rfc/rfc2779.txt>.
[3] Jabber Software Foundation, "Jabber Software Foundation", August
2001, <http://www.jabber.org/>.
[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, <http://
www.ietf.org/rfc/rfc2778.txt>.
[6] Dawson, F. and T. Howes, "vCard MIME Directory Profile", RFC
2426, September 1998.
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
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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>
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<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.
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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>
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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='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='list'>
<xsd:complexType>
<xsd:choice minOccurs='0' maxOccurs='unbounded'>
<xsd:element ref='item' minOccurs='0' maxOccurs='unbounded'/>
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</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' minOccurs='0' maxOccurs='1'/>
</xsd:choice>
<xsd:attribute name='jid' type='xsd:string' use='required'/>
<xsd:attribute name='type' 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='subscription' use='optional'>
<xsd:simpleType>
<xsd:restriction base='xsd:NCName'>
<xsd:enumeration value='to'/>
<xsd:enumeration value='from'/>
<xsd:enumeration value='both'/>
</xsd:restriction>
</xsd:simpleType>
</xsd:attribute>
</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'>
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<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.
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<?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?,
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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. -->
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<!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. -->
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<!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)>
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<!-- 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)>
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<!-- 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>
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<!-- Format type parameter. -->
<!ELEMENT TYPE (#PCDATA)>
<!-- Base64 encoded binary value. -->
<!ELEMENT BINVAL (#PCDATA)>
<!-- URI to external binary value -->
<!ELEMENT EXTVAL (#PCDATA)>
<!-- ==== -->
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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-02
o Added a great deal more detail to the narrative regarding
server-side privacy rules as well as the interaction between
rosters and subscriptions.
o Removed DTDs in favor of schemas (with the exception of vCard
XML).
o Removed non-normative documentation of authentication using
jabber:iq:auth and of in-band registration using
jabber:iq:register, since these are maintained by the Jabber
Software Foundation and are not part of the XMPP specification.
C.2 Changes from draft-ietf-xmpp-im-01
o Made numerous small editorial changes.
C.3 Changes from draft-ietf-xmpp-im-00
o Moved registration and authentication via jabber:iq:auth to
non-normative appendices.
o Changed initial presence stanza from MUST be empty to SHOULD be
empty.
o Specified that user or clients should not send presence stanzas of
type 'probe'.
o Specified the algorithm for digest passwords.
C.4 Changes from draft-miller-xmpp-im-02
o Added information about the 'jabber:iq:last' protocol to meet the
requirement defined in section 3.2.4 of RFC 2779.
o Added information about the 'jabber:iq:privacy' protocol to meet
the requirement defined in section 2.3.5 of RFC 2779.
o Added information about the vCard XML protocol to meet the
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requirement defined in sections 3.1.3 and 4.1.4 of RFC 2779.
o Changed the material describing authentication (but not resource
authorization) with 'jabber:iq:auth' to non-normative.
o Noted that the only watchers are subscribers.
o Nomenclature changes: (1) from "chunks" to "stanzas"; (2) from
"host" to "server"; (3) from "node" to "client" or "user" (as
appropriate).
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Intellectual Property Statement
The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances of
licenses to be made available, or the result of an attempt made to
obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification can
be obtained from the IETF Secretariat.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive
Director.
Full Copyright Statement
Copyright (C) The Internet Society (2003). 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 implementation 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 assignees.
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
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
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