Network Working Group                                     P. Saint-Andre
Internet-Draft                                                 J. Miller
Expires: November 2, 2003                     Jabber Software Foundation
                                                            May 04, 2003


                         XMPP Instant Messaging
                         draft-ietf-xmpp-im-11

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
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   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
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   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.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on November 2, 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
   required to create a basic instant messaging and presence
   application, such as the servers and clients that comprise the Jabber
   network.










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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.    Establishing a Session . . . . . . . . . . . . . . . . . . .  6
   3.    Exchanging Messages  . . . . . . . . . . . . . . . . . . . .  8
   3.1   Specifying an Intended Recipient . . . . . . . . . . . . . .  8
   3.2   Specifying a Message Type  . . . . . . . . . . . . . . . . .  8
   3.3   Specifying a Message Body  . . . . . . . . . . . . . . . . .  9
   3.4   Specifying a Message Subject . . . . . . . . . . . . . . . .  9
   3.5   Specifying a Conversation Thread . . . . . . . . . . . . . . 10
   4.    Exchanging Presence Information  . . . . . . . . . . . . . . 12
   4.1   Client and Server Responsibilities . . . . . . . . . . . . . 12
   4.2   Specifying Availability Status . . . . . . . . . . . . . . . 15
   4.3   Specifying Detailed Status Information . . . . . . . . . . . 15
   4.4   Determining When a Contact Went Offline  . . . . . . . . . . 16
   4.5   Presence Examples  . . . . . . . . . . . . . . . . . . . . . 17
   5.    Managing Subscriptions . . . . . . . . . . . . . . . . . . . 22
   5.1   Requesting a Subscription  . . . . . . . . . . . . . . . . . 22
   5.2   Handling a Subscription Request  . . . . . . . . . . . . . . 22
   5.3   Cancelling a Subscription from Another Entity  . . . . . . . 23
   5.4   Unsubscribing from Another Entity's Presence . . . . . . . . 23
   6.    Managing One's Roster  . . . . . . . . . . . . . . . . . . . 24
   6.1   Retrieving One's Roster on Login . . . . . . . . . . . . . . 24
   6.2   Adding a Roster Item . . . . . . . . . . . . . . . . . . . . 25
   6.3   Updating a Roster Item . . . . . . . . . . . . . . . . . . . 27
   6.4   Deleting a Roster Item . . . . . . . . . . . . . . . . . . . 27
   7.    Integration of Roster Items and Presence Subscriptions . . . 29
   7.1   Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 29
   7.2   User Subscribes to Contact . . . . . . . . . . . . . . . . . 29
   7.2.1 Alternate Flow: Contact Declines Subscription Request  . . . 32
   7.3   Creating a Mutual Subscription . . . . . . . . . . . . . . . 33
   7.3.1 Alternate Flow: User Declines Subscription Request . . . . . 35
   7.4   Unsubscribing  . . . . . . . . . . . . . . . . . . . . . . . 36
   7.4.1 Case #1: Subscription Type 'to'  . . . . . . . . . . . . . . 36
   7.4.2 Case #2: Subscription Type 'both'  . . . . . . . . . . . . . 38
   7.5   Cancelling a Subscription  . . . . . . . . . . . . . . . . . 40
   7.5.1 Case #1: Subscription Type 'from'  . . . . . . . . . . . . . 40
   7.5.2 Case #2: Subscription Type 'both'  . . . . . . . . . . . . . 41
   7.6   Removing a Roster Item and Cancelling All Subscriptions  . . 42
   8.    Blocking Communication . . . . . . . . . . . . . . . . . . . 44
   8.1   Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
   8.2   Business Rules . . . . . . . . . . . . . . . . . . . . . . . 46
   8.3   Retrieving One's Privacy Lists . . . . . . . . . . . . . . . 47



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   8.4   Managing Active Lists  . . . . . . . . . . . . . . . . . . . 50
   8.5   Managing the Default List  . . . . . . . . . . . . . . . . . 52
   8.6   Editing a Privacy List . . . . . . . . . . . . . . . . . . . 53
   8.7   Adding a New Privacy List  . . . . . . . . . . . . . . . . . 53
   8.8   Removing a Privacy List  . . . . . . . . . . . . . . . . . . 54
   8.9   Blocking Messages  . . . . . . . . . . . . . . . . . . . . . 54
   8.10  Blocking Inbound Presence Notifications  . . . . . . . . . . 56
   8.11  Blocking Outbound Presence Notifications . . . . . . . . . . 58
   8.12  Blocking IQs . . . . . . . . . . . . . . . . . . . . . . . . 59
   8.13  Blocking All Communication . . . . . . . . . . . . . . . . . 61
   8.14  Blocked Entity Attempts to Communicate with User . . . . . . 62
   8.15  Higher-Level Heuristics  . . . . . . . . . . . . . . . . . . 63
   9.    Server Rules for Handling XML Stanzas  . . . . . . . . . . . 65
   9.1   No 'to' Address  . . . . . . . . . . . . . . . . . . . . . . 65
   9.2   Foreign Domain . . . . . . . . . . . . . . . . . . . . . . . 65
   9.3   Subdomain  . . . . . . . . . . . . . . . . . . . . . . . . . 65
   9.4   Bare Domain or Specific Resource . . . . . . . . . . . . . . 65
   9.5   User in Same Domain  . . . . . . . . . . . . . . . . . . . . 66
   10.   IANA Considerations  . . . . . . . . . . . . . . . . . . . . 68
   10.1  XML Namespace Name for Session Data  . . . . . . . . . . . . 68
   11.   Security Considerations  . . . . . . . . . . . . . . . . . . 69
         Normative References . . . . . . . . . . . . . . . . . . . . 70
         Informative References . . . . . . . . . . . . . . . . . . . 71
         Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 71
   A.    vCards . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
   B.    XML Schemas  . . . . . . . . . . . . . . . . . . . . . . . . 73
   B.1   session  . . . . . . . . . . . . . . . . . . . . . . . . . . 73
   B.2   jabber:iq:last . . . . . . . . . . . . . . . . . . . . . . . 73
   B.3   jabber:iq:privacy  . . . . . . . . . . . . . . . . . . . . . 73
   B.4   jabber:iq:privacy:error  . . . . . . . . . . . . . . . . . . 75
   B.5   jabber:iq:roster . . . . . . . . . . . . . . . . . . . . . . 75
   C.    Revision History . . . . . . . . . . . . . . . . . . . . . . 77
   C.1   Changes from draft-ietf-xmpp-im-10 . . . . . . . . . . . . . 77
   C.2   Changes from draft-ietf-xmpp-im-09 . . . . . . . . . . . . . 77
   C.3   Changes from draft-ietf-xmpp-im-08 . . . . . . . . . . . . . 77
   C.4   Changes from draft-ietf-xmpp-im-07 . . . . . . . . . . . . . 77
   C.5   Changes from draft-ietf-xmpp-im-06 . . . . . . . . . . . . . 78
   C.6   Changes from draft-ietf-xmpp-im-05 . . . . . . . . . . . . . 78
   C.7   Changes from draft-ietf-xmpp-im-04 . . . . . . . . . . . . . 78
   C.8   Changes from draft-ietf-xmpp-im-03 . . . . . . . . . . . . . 78
   C.9   Changes from draft-ietf-xmpp-im-02 . . . . . . . . . . . . . 79
   C.10  Changes from draft-ietf-xmpp-im-01 . . . . . . . . . . . . . 79
   C.11  Changes from draft-ietf-xmpp-im-00 . . . . . . . . . . . . . 79
   C.12  Changes from draft-miller-xmpp-im-02 . . . . . . . . . . . . 79
         Intellectual Property and Copyright Statements . . . . . . . 81






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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 required to
   create the basic functionality expected of an instant messaging and
   presence application as defined in 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 use cases:

   o  Establish a session 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], and the interested reader is directed to that document
   regarding the requirements addressed herein.

   Note: although XMPP IM meets the requirements of RFC 2779, 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. In addition, protocols
   addressing many other functionality areas have been defined and
   continue to be defined by the Jabber Software Foundation [4]. These
   include service discovery, multi-user chat, data gathering and forms
   submission, feature negotiation, message composing events, message
   expiration, delayed delivery, file transfer, XHTML message
   formatting, publish-subscribe, and transports for XML-RPC and SOAP.



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   However, such protocols are not described herein because they are not
   required by RFC 2779 [2].

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 [3].

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. Establishing a Session

   Most instant messaging applications based on XMPP are implemented via
   a client-server architecture that requires a user to establish a
   session on the server in order to engage in the expected instant
   messaging and presence activities. However, there are several
   pre-conditions that must be met before a user may establish such a
   session. These include:

   1.  Account Provisioning -- while this 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 documented
       by the Jabber Software Foundation [4] at <http://www.jabber.org/
       protocol/>.

   2.  Authentication and Resource Authorization -- methods for
       completing these pre-conditions are documented in XMPP Core [1];
       note that client authentication with a server MUST include an
       authorization identity that specifies the full JID (user@domain/
       resource) associated with the connection for addressing purposes.

   Once a client has authenticated with a server and authorized a full
   JID (including resource), it SHOULD request that the server activate
   an IM session for the client. This is accomplished by means of the
   'urn:ietf:params:xml:ns:xmpp-session' namespace:

   Step 1: Client requests session with server:

   <iq type='set' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
   </iq>

   Step 2: Server informs client that session has been created:

   <iq type='result' id='sess_1'/>

   Several error conditions are possible. For example, the server may
   encounter an internal condition that prevents it from creating the
   session, the username or authorization identity may lack permissions
   to create a session, or there may already be an active session
   associated with an authzid of the same name.

   If the server encounters an internal condition that prevents it from
   creating the session, it MUST return an error.






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   Step 2 (alt): Server responds with error (internal server error):

   <iq type='error' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
     <error class='server'>
       <condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
         <internal-server-error/>
       </condition>
     </error>
   </iq>

   If the username or authorization identity is not allowed to create a
   session, the server MUST return an error.

   Step 2 (alt): Server responds with error (username or authzid not
   allowed to create session):

   <iq type='error' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
     <error class='access'>
       <condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
         <not-allowed/>
       </condition>
     </error>
   </iq>

   If there is already an active session associated with an authzid of
   the same name, the server MUST either (1) terminate the active
   session and allow the newly-requested session, or (2) disallow the
   newly-requested session and maintain the existing session. Which of
   these the server does is up to the implementation, although it is
   RECOMMENDED to implement (1).

   Step 2 (alt): Server informs client of resource conflict (the desired
   resource name is already in use by another active connection):

   <iq type='error' id='sess_1'>
     <session xmlns='urn:ietf:params:xml:ns:xmpp-session'/>
     <error class='access'>
       <condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
         <conflict/>
       </condition>
     </error>
   </iq>







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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 Section 9, 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).

   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

   An IM client SHOULD specify an intended recipient for a message by
   providing the JID of an entity other than the sender in the 'to'
   attribute of the <message/> stanza. If the message is being sent in
   reply to a message previously received from an address of the form
   <user@domain/resource> (e.g., within the context of a chat session),
   the value of the 'to' address SHOULD be the complete address rather
   than merely <user@domain> unless the sender has knowledge (via
   presence) that the intended recipient is no longer available. If the
   message is being sent outside the context of any existing chat
   session or received message, the value of the 'to' address SHOULD be
   of the form <user@domain> rather than <user@domain/resource>.

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 no 'type' attribute is
   provided, the message SHOULD be assumed to be a standalone message to
   which the recipient MAY reply if desired. If the 'type' attribute is
   included, it 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. A compliant client SHOULD present an interface
      enabling one-to-one chat between the two parties, including an
      appropriate conversation history.

   o  groupchat -- The message is sent in the context of a multi-user
      chat environment. A compliant client SHOULD present an interface
      enabling many-to-many chat between the parties, including a roster
      of parties in the chatroom and an appropriate conversation



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      history.

   o  headline -- The message is probably generated by an automated
      service that delivers or broadcasts content (news, sports, market
      information, RSS feeds, etc.). No reply to the message is
      expected, and a compliant client SHOULD present an interface that
      appropriately differentiates the message from standalone messages,
      chat sessions, or groupchat sessions (e.g., by not providing the
      recipient with the ability to reply).

   o  error -- An error has occurred related to a previous message sent
      by the sender (for details regarding stanza error syntax, see XMPP
      Core [1]). A compliant client SHOULD present an appropriate
      interface informing the sender of the nature of the error.

   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 Body

   A message stanza MAY (and often will) contain a child <body/> element
   specifying the main content of the message. The contents of the body
   MUST be XML character data and 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 some other
   child of the message stanza. Multiple <body/> elements MAY be
   included, as long as each such element possesses an 'xml:lang'
   attribute with a distinct value.

   A message with a body:

   <message to='romeo@montague.net' from="juliet@capulet.com/balcony'>
     <body xml:lang='en'>Wherefore art thou, Romeo?</body>
     <body xml:lang='cz'>Pro&#x010D;e&#x017D; jsi ty, Romeo?</body>
   </message>


3.4 Specifying a Message Subject

   A message stanza MAY contain one or more child <subject/> elements
   specifying the topic of the message. A subject element MUST contain
   XML character data and MUST NOT contain mixed content. Multiple
   <subject/> elements MAY be included, as long as each such element
   possesses an 'xml:lang' attribute with a distinct value.



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   A message with a subject:

   <message to='romeo@montague.net' from="juliet@capulet.com/balcony'>
     <subject xml:lang='en'>
       I implore you!
     </subject>
     <subject xml:lang='cz'>
       &#00DA;p&#x011B;nliv&#x011B; prosim!
     </subject>
     <body xml:lang='en'>
       Wherefore art thou, Romeo?
     </body>
     <body xml:lang='cz'>
       Pro&#x010D;e&#x017D; jsi ty, Romeo?
     </body>
   </message>


3.5 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.

























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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>


























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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 its 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.)

   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 its server, it SHOULD send an initial
   presence stanza to the server in order to signal its availability for
   communications. The initial 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 possess no 'type' attribute.

   Upon receiving initial presence from a client, the user's server MUST
   do the following:

   1.  Send presence probes (i.e., presence stanzas whose 'type'
       attribute is set to a value of "probe") from the full JID
       (user@domain/resource) of the user to the bare JID (user@domain)
       of any contacts to which the user is subscribed in order to
       determine if they are available; such contacts are those which
       are present in the user's roster with the 'subscription'
       attribute set to a value of "to" or "both". (Note: a user or
       client SHOULD NOT send presence probes.)

   2.  Broadcast initial presence from the full JID (user@domain/
       resource) of the user to the bare JID (user@domain) of any
       contacts that are subscribed to the user's presence; such
       contacts are those which are present in the user's roster with
       the 'subscription' attribute set to a value of "from" or "both".

   Upon receiving a presence probe from the user, the contact's server
   MUST do one of the following:

   1.  If the username specified in the 'to' address of the presence
       probe does not exist, return an <item-not-found/> error to the
       user.




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   2.  Else if the user is not in the contact's roster with a
       subscription state of "from" or "both", return a
       <recipient-unavailable/> stanza error to the user.

   3.  Else if the contact has no active sessions, return a
       <recipient-unavailable/> error to the user.

   4.  Else if the contact has blocked outbound presence notifications
       to the user's bare or full JID (as defined in Section 8.11),
       return a <recipient-unavailable/> error to the user.

   5.  Else send to the user the last known availability information
       (i.e., the full XML of the last presence stanza) provided by each
       of the contact's active sessions.

   Upon receiving initial presence from the user, the contact's server
   MUST do one of the following:

   1.  If the username specified in the 'to' address does not exist,
       return an <item-not-found/> error to the user.

   2.  Else if the user is not in the contact's roster with a
       subscription state of "to" or "both", return a
       <recipient-unavailable/> stanza error to the user.

   3.  Else if the contact has no active sessions, return a
       <recipient-unavailable/> error to the user.

   4.  Else if the contact has blocked inbound presence notifications
       from the user's bare or full JID (as defined in Section 8.10),
       return a <recipient-unavailable/> error to the user.

   5.  Else deliver the user's presence stanza to the full JIDs
       (contact@domain/resource) associated with all of the contact's
       active sessions (subject to privacy rules).

   If the user's server receives a presence stanza of type "error" in
   response to the initial presence that it forwarded to a contact on
   behalf of the user, it MUST NOT send further presence updates to that
   contact (until and unless it successfully sends subsequent presence
   information to that contact, whether or not in response to a presence
   probe from the contact).

   After sending initial presence, the user MAY update and broadcast its
   presence information at any point during its active session by
   sending a presence stanza with no 'to' address and either no 'type'
   attribute or a 'type' attribute with a value of "unavailable". (Note:
   a user's client SHOULD NOT send a presence update to broadcast



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   information that changes independently of the user's presence and
   availability.) If the presence stanza lacks a 'type' attribute (i.e.,
   expresses availability), the user's server MUST broadcast the full
   XML of that presence stanza to all contacts that are in the user's
   roster with a subscription type of "from" or "both" and from whom the
   server has not received a presence error during the user's session.
   If the presence stanza has a 'type' attribute set to a value of
   "unavailable", the user's server MUST broadcast the full XML of that
   presence stanza to all contacts that are in the user's roster with a
   subscription type of "from" or "both" and from whom the server has
   not received a presence error during the user's session, as well as
   to any entities to which the user has sent directed presence during
   the user's session.

   A user MAY send directed presence to another entity (i.e., a presence
   stanza with a 'to' attribute whose value is the JID of the other
   entity and with either no 'type' attribute or a 'type' attribute
   whose value is "unavailable"). There are three possible cases:

   1.  If the user sends directed presence to a contact that is in the
       user's roster with a subscription type of "from" or "both" after
       having sent initial presence and before sending unavailable
       presence broadcast, the user's server MUST route or deliver the
       full XML of that presence stanza but SHOULD NOT otherwise modify
       the contact's status regarding presence broadcast (i.e., it
       SHOULD include the contact's JID in any subsequent presence
       broadcasts initiated by the user).

   2.  If the user sends directed presence to an entity that is not in
       the user's roster with a subscription type of "from" or "both"
       after having sent initial presence and before sending unavailable
       presence broadcast, the user's server MUST route or deliver the
       full XML of that presence stanza to the entity but MUST NOT
       modify the contact's status regarding available presence
       broadcast (i.e., it MUST NOT include the entity's JID in any
       subsequent broadcasts of available presence initiated by the
       user); however, if the connected resource from which the user
       sent the directed presence become unavailable, the user's server
       MUST broadcast that unavailable presence to the entity.

   3.  If the user sends directed presence without ever first sending
       initial presence or after having sent unavailable presence
       broadcast, the user's server MUST treat the entities to which the
       user sends directed presence in the same way that it treats the
       entities listed in Case 2 above.

   Before ending its session with a server, a client SHOULD gracefully
   become unavailable by sending a final presence stanza that is



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   explicitly of type unavailable (optionally, final presence MAY
   contain one or more <status/> elements specifying the reason why the
   user is no longer available). However, the user's server MUST NOT
   depend on receiving final presence from a connected resource, since
   the resource may become unavailable unexpectedly. If the user's
   server detects that one of the user's resources has become
   unavailable for any reason (either gracefully or ungracefully), it
   MUST broadcast unavailable presence, the user's server MUST broadcast
   unavailable presence to all contacts that are in the user's roster
   with a subscription type of "from" or "both" and from whom the server
   has not received a presence error during the session, as well as to
   any entities to which the user has sent directed presence during the
   user's session for that resource.

4.2 Specifying Availability Status

   A client MAY provide further information about its availability
   status by using the <show/> element. As mentioned in XMPP Core [1],
   the recognized values for the show element are:

   o  away -- The entity or resource is temporarily away.

   o  chat -- The entity or resource is actively interested in chatting.

   o  xa -- The entity or resource is away for an extended period (xa =
      "eXtended Away").

   o  dnd -- The entity or resource is busy (dnd = "Do Not Disturb").

   Availability status:

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

   If no <show/> element is provided, the entity is assumed to be online
   and available.

4.3 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.







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   Detailed status information:

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


4.4 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 request 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 (i.e., exists in the user's roster
   with the 'subscription' attribute set to a value of "from" or "both")
   and the user is not blocking IQ stanzas to and from the entity (as
   defined in Section 8.12), the server SHOULD return an IQ stanza of
   type "result" with the number of seconds since the user was last
   active (if the user is online and available, the 'seconds' attribute
   should be set to a value of "0", i.e., zero):

   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 (i.e., does not exist in
   the user's roster with the 'subscription' attribute set to a value of
   "from" or "both"), the server MUST return an IQ stanza of type
   "error" with an error condition of forbidden:








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

   <iq from='user@domain' type='error' to='subscriber@domain/resource'>
     <query xmlns='jabber:iq:last'/>
     <error class='access'>
       <condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
         <forbidden/>
       </condition>
     </error>
   </iq>


4.5 Presence Examples

   The examples in this section illustrate the presence-related
   protocols described above. The user is romeo@montague.net, he has
   authorized a resource "orchard", and he has the following individuals
   in his roster:

   o  juliet@capulet (subscription="both" and she has two active
      sessions, one whose resource is "chamber" and another whose
      resource is "balcony")

   o  benvolio@shakespeare.lit (subscription="to")

   o  mercutio@shakespeare.lit (subscription="from")

   Example 1: User sends initial presence:

   <presence/>

   Example 2: User's server sends presence probe to contacts with
   subscription="to" and subscription="both" on behalf of the user's
   connected resource:

   <presence
       type='probe'
       from='romeo@montague.net/orchard'
       to='juliet@capulet.com'/>

   <presence
       type='probe'
       from='romeo@montague.net/orchard'
       to='benvolio@shakespeare.lit'/>







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   Example 3: User's server sends initial presence to contacts with
   subscription="from" and subscription="both" on behalf of the user's
   connected resource:

   <presence
       from='romeo@montague.net/orchard'
       to='juliet@capulet.com'/>

   <presence
       from='romeo@montague.net/orchard'
       to='mercutio@shakespeare.lit'/>

   Example 4: Contacts' servers reply to presence probe on behalf of all
   of the contacts' connected resources:

   <presence
       from='juliet@capulet.com/balcony'
       to='romeo@montague.net/orchard'>
     <show>away</show>
     <status>be right back</status>
     <priority>0</priority>
   </presence>

   <presence
       from='juliet@capulet.com/chamber'
       to='romeo@montague.net/orchard'>
     <priority>1</priority>
   </presence>

   <presence
       from='benvolio@shakespeare.lit/pda'
       to='romeo@montague.net/orchard'>
     <show>dnd</show>
     <status>gallivanting</status>
     <priority>2</priority>
   </presence>















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   Example 5: Contacts' servers deliver user's initial presence to all
   of the contacts' connected resources or returns error to user:

   <presence
       from='romeo@montague.net/orchard'
       to='juliet@capulet.com/chamber'/>

   <presence
       from='romeo@montague.net/orchard'
       to='juliet@capulet.com/balcony'/>

   <presence
       type='error'
       from='mercutio@shakespeare.lit'
       to='romeo@montague.net/orchard'>
     <error class='recipient'>
       <condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
         <recipient-unavailable/>
       </condition>
     </error>
     </error>
   </presence>

   Example 6: User sends directed presence to another user not in his
   roster:

   <presence
       from='romeo@montague.net/orchard'
       to='nurse@capulet.com'>
     <show>dnd</show>
     <status>courting Juliet</status>
     <priority>0</priority>
   </presence>

   Example 7: User sends updated available presence information for
   broadcasting:

   <presence>
     <show>away</show>
     <status>I shall return!</status>
     <priority>1</priority>
   </presence>









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   Example 8: Updated presence information is delivered only to one
   contact (not those from whom an error was received or to whom the
   user sent directed presence):

   <presence
       from='romeo@montague.net/orchard'
       to='juliet@capulet.com/chamber'>
     <show>away</show>
     <status>I shall return!</status>
     <priority>1</priority>
   </presence>

   <presence
       from='romeo@montague.net/orchard'
       to='juliet@capulet.com/balcony'>
     <show>away</show>
     <status>I shall return!</status>
     <priority>1</priority>
   </presence>

   Example 9: One of the contact's resources sends final presence:

   <presence type='unavailable'/>

   Example 10: Unavailable presence information is delivered from
   contact to user:

   <presence
       type='unavailable'
       from='juliet@capulet.com/balcony'
       to='romeo@montague.net/orchard'/>

   Example 11: User sends final presence:

   <presence type='unavailable'>
     <status>gone home</status>
   </presence>














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   Example 12: Unavailable presence information is delivered to
   contact's one remaining resource as well as to the other person to
   whom the user sent directed presence:

   <presence
       type='unavailable'
       from='romeo@montague.net/orchard'
       to='juliet@capulet.com/chamber'>
     <status>gone home</status>
   </presence>

   <presence
       from='romeo@montague.net/orchard'
       to='nurse@capulet.com'>
     <status>gone home</status>
   </presence>



































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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 disclosed
   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. A
   subscription lasts across sessions; indeed, it lasts until the
   subscriber unsubscribes or the subscribee cancels the
   previously-granted subscription. Subscriptions are managed within
   XMPP by sending presence stanzas containing specially-defined
   attributes.

   Note: there are important interactions between subscriptions and
   rosters; these are defined under Integration of Roster Items and
   Presence Subscriptions (Section 7), and the reader must refer to that
   section for a complete understanding of 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'/>

   If the subscription request is being sent another IM user, the JID
   supplied in the 'to' attribute SHOULD be of the form <user@domain>
   rather than <user@domain/resource>.

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



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   the user's client. If there is no connected resource associated with
   the user when the subscription request is received by the server, 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, which consists of any
   number of specific roster items, each roster item being identified by
   a unique JID of the form "contact@domain". A user's roster is stored
   by the user's server on the user's behalf so that the user may access
   roster information from any connected resource.

   Note: there are important interactions between rosters and
   subscriptions; these are defined under Integration of Roster Items
   and Presence Subscriptions (Section 7), and the reader must refer to
   that section for a complete understanding of roster management.

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). 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>
























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   Client receives roster from the server:

   <iq
       from='juliet@capulet.com/balcony'
       to='juliet@capulet.com/balcony'
       id='roster_1'
       type='result'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='romeo@montague.net'
           name='Romeo'
           subscription='both'>
         <group>Friends</group>
       </item>
       <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 value of the 'jid' attribute SHOULD be of the form <user@domain>,
   especially if the item is associated with another (human) IM user.



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   The server MUST update the roster information in persistent storage,
   and also push the 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='juliet@capulet.com/balcony'
       to='juliet@capulet.com/balcony'
       type='result'
       id='roster_2'/>
   <iq
       from='juliet@capulet.com/balcony'
       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='juliet@capulet.com/balcony'
       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>











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   Connected resources reply with an IQ result to the server:

   <iq
       from='juliet@capulet.com/balcony'
       to='capulet.com'
       type='result'/>
   <iq
       from='juliet@capulet.com/chamber'
       to='capulet.com'
       type='result'/>


6.3 Updating a Roster Item

   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.

   User updates roster item (added group):

   <iq type='set' id='roster_3'>
     <query xmlns='jabber:iq:roster'>
       <item
           jid='romeo@montague.net'
           name='Romeo'
           subscription='both'>
         <group>Friends</group>
         <group>Lovers</group>
       </item>
     </query>
   </iq>

   As with adding a roster item, when updating a roster item the server
   MUST update the roster information in persistent storage, and also
   initiate a "roster push" to all connected resources associated with
   the user.

6.4 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).








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   Client removes an item:

   <iq type='set' id='roster_4'>
     <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
   MUST update the roster information in persistent storage, and also
   initiate 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 (i.e., the union of 'from' and 'to')

   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 are 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. In addition, a client MUST acknowledge
   each "roster push" with an IQ stanza of type "result" (these stanzas
   are not shown in the following examples but are required by XMPP Core
   [1]).

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 SHOULD 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 one or more <group/>
       child, and MUST NOT posses a 'subscription' attribute:



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   <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:














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

       Note: if the user did not create a roster item before sending the
       subscription request, the server MUST now create one and send the
       above "roster push" to all of the user's connected resources.

   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 (i.e.,
       <user@domain>) 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 request (the alternate flow of
       declining the subscription request is defined in Section 7.2.1).
       In this 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
       in order to accept the subscription request.

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

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





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   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' attribute 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 silently ignore that request and not send it on
   the contact.)

7.2.1 Alternate Flow: Contact Declines Subscription Request

   The above activity flow represents the "happy path" related to the
   user's subscription request to the contact. The main alternate flow



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

   1.  If the contact desires a mutual subscription, 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:





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   <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 request (the alternate flow of declining the
       subscription request is defined in Section 7.3.1). In this case,
       the user's client MUST send a presence stanza of
       type='subscribed' to the contact in order to accept the
       subscription request.

   <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' attribute set to
       a value of "both":






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   <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 MUST silently ignore that request
   and not send it on the intended recipient.)

7.3.1 Alternate Flow: User Declines Subscription Request

   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 contact'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:















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   <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 'subscription' attribute set to a
       value of "none":








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

   3.  The user's server MUST also route the unsubscribe "command" to
       the contact's server:

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

   4.  The contact's server 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); the contact's
       server SHOULD also deliver the unsubscribe command to the
       contact:

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

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

   5.  The contact's server then MUST send unavailable presence from the
       contact to the user and MAY send a presence stanza of type
       "unsubscribed" to the user:








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

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

   6.  As a result, the user's server MUST deliver the unavailable
       presence from the user to the contact and (if received) the
       presence stanza of type "unsubscribed" from the contact to the
       user,

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

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


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 'subscription' attribute set to a
       value of "from":

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



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   </iq>

   3.  The contact's server then SHOULD auto-reply on behalf of the
       contact by sending a presence stanza of type "unsubscribed" to
       the user; additionally, it MUST send unavailable presence from
       the contact to the user:

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

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

   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, the user's server MUST (1) deliver the presence
       stanza of type='unsubscribed' from the contact to the user and
       (3) deliver the unavailable presence from the user to the
       contact:

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

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




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   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'

   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 (1) 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", and (2) send unavailable
       presence from the contact to the user:

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

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





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   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); additionally, it MUST also deliver
       the unavailable presence from the contact to the user:

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

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


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 (1) 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", and (2) send unavailable
       presence from the contact to the user:













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

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

   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); additionally, it MUST also deliver
       the unavailable presence from the contact to the user:

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

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

   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



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   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. As a
   result of this command, the user's server must send the user a
   "roster push" with the subscription state set to "none", and the
   contact's server must do the same.

   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.

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

   o  Retrieving 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 (i.e., the list
      that is active by default).

   o  Allowing or denying messages based on JID, group, or subscription
      type (or globally).

   o  Allowing or denying inbound presence notifications based on JID,
      group, or subscription type (or globally).

   o  Allowing or denying outbound presence notifications 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).

   Note: 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 rules 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.



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   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/resource>, then <domain>.
   If the value is <user@domain>, then any connected resource for that
   user@domain matches. If the value is <domain/resource>, then only
   that resource matches. If the value is <domain>, then any user@domain
   (or subdomain) matches.

   If the type is "group", then the 'value' attribute MUST contain the
   name of a group in the user's roster. (If a client attempts to update
   or delete a list item with a group that is not in the user's roster,
   the server MUST return to the client an <item-not-found/> error of
   class "address" in the 'urn:ietf:params:xml:ns:xmpp-stanzas'
   namespace.)

   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 to the client a <bad-request/> error
   of class "format" in the 'urn:ietf:params:xml:ns:xmpp-stanzas'
   namespace.

   Within the 'jabber:iq:privacy' namespace, the <query/> child of a
   client-generated IQ stanza of type "set" MUST NOT include more than
   one child element (i.e., the stanza must contain only one <active/>



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   element, one <default/> element, or one <list/> element); if a client
   violates this rule, the server MUST return to the client a
   <bad-request/> error of class "format" in the
   'urn:ietf:params:xml:ns:xmpp-stanzas' namespace.)

   When a client adds or updates a privacy list, the <list/> element
   MUST contain at least one <item/> child element; if a client violates
   this rule, the server MUST return to the client a <bad-request/>
   error of class "format" in the 'urn:ietf:params:xml:ns:xmpp-stanzas'
   namespace.

   When a client updates a privacy list, it must include all of the
   desired items (i.e., not a "delta").

8.2 Business Rules

   The active list affects only the session/resource for which it is
   activated, and only for the duration of the session. If a stanza is
   addressed to a specific resource, only the active list for that
   session is processed (i.e., the default list is ignored).

   The default list applies to the user as a whole, and is processed if
   there is no active list set for the target session/resource to which
   a stanza is addressed, or if there are no current sessions for the
   user.

   If there is no active list set for a session (or there are no current
   sessions for the user), and there is no default list, then all
   stanzas SHOULD BE accepted or appropriately processed by the server
   on behalf of the user.

   Privacy lists SHOULD be the first routing and delivery rule applied
   by a server, trumping the other rules specified in Section 9.

   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
   SHOULD 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".

   When a user updates the definition for a list or adds a new list
   (whether or not it is active), the server SHOULD NOT "push" that
   information out to all connected resources associated with the user's
   account, as is done for rosters. If a client or user wants to



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   retrieve the current privacy list information, it SHOULD request the
   relevant list.

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'>
       <active name='private'/>
       <default name='public'/>
       <list name='public'/>
       <list name='private'/>
       <list name='special'/>
     </query>
   </iq>

   Client requests a privacy list from server:

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

   Server sends a privacy list 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' action='deny' order='1'/>
         <item action='allow' order='2'/>
       </list>
     </query>
   </iq>









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   Client requests another privacy list from server:

   <iq type='get' id='getlist3'>
     <query xmlns='jabber:iq:privacy'>
       <list name='private'/>
     </query>
   </iq>

   Server sends another privacy list to client:

   <iq type='result' id='getlist3' to='romeo@montague.net/orchard'>
     <query xmlns='jabber:iq:privacy'>
       <list name='private'>
         <item type='subscription' value='both'
               action='allow' order='10'/>
         <item action='deny' order='15'/>
       </list>
     </query>
   </iq>

   Client requests yet another privacy list from server:

   <iq type='get' id='getlist4'>
     <query xmlns='jabber:iq:privacy'>
       <list name='special'/>
     </query>
   </iq>
























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   Server sends yet another privacy list to client:

   <iq type='result' id='getlist4' to='romeo@montague.net/orchard'>
     <query xmlns='jabber:iq:privacy'>
       <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
   bidirectional 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.

   If the user attempts to retrieve a list but a list by that name does
   not exist, the server MUST return an "item not found" stanza error to
   the user, which SHOULD include a <no-such-list/> child element scoped
   by the 'jabber:iq:privacy:error' namespace:















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   Client attempts to retrieve non-existent list:

   <iq type='error' id='getlist5'>
     <query xmlns='jabber:iq:privacy'>
       <list name='The Empty Set'/>
     </query>
     <error class='address'>
       <condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
         <item-not-found>
           <no-such-list xmlns='jabber:iq:privacy:error'/>
         </item-not-found>
       </condition>
     </error>
   </iq>

   The user is allowed to retrieve only one list at a time. If the user
   attempts to retrieve more than one list in the same request, the
   server MUST return a "bad request" stanza error to the user, which
   SHOULD include a <too-many-lists/> child element scoped by the
   'jabber:iq:privacy:error' namespace:

   Client attempts to retrieve more than one list:

   <iq type='error' id='getlist6'>
     <query xmlns='jabber:iq:privacy'>
       <list name='public'/>
       <list name='private'/>
       <list name='special'/>
     </query>
     <error class='format'>
       <condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
         <bad-request>
           <too-many-lists xmlns='jabber:iq:privacy:error'/>
         </bad-request>
       </condition>
     </error>
   </iq>


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.





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   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 back to the client.

   Server acknowledges success of active list change:

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

   If the user attempts to set an active list but a list by that name
   does not exist, the server MUST return an "item not found" stanza
   error to the user, which SHOULD include a <no-such-list/> child
   element scoped by the 'jabber:iq:privacy:error' namespace:

   Client attempts to set a non-existent list as active:

   <iq type='error' id='active2'>
     <query xmlns='jabber:iq:privacy'>
       <list name='The Empty Set'/>
     </query>
     <error class='address'>
       <condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
         <item-not-found>
           <no-such-list xmlns='jabber:iq:privacy:error'/>
         </item-not-found>
       </condition>
     </error>
   </iq>

   In order to decline the use of any active list, 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>






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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'/>

   If the user attempts to set a default list but a list by that name
   does not exist, the server MUST return an "item not found" stanza
   error to the user, which SHOULD include a <no-such-list/> child
   element scoped by the 'jabber:iq:privacy:error' namespace:

   Client attempts to set a non-existent list as default:

   <iq type='error' id='default2'>
     <query xmlns='jabber:iq:privacy'>
       <list name='The Empty Set'/>
     </query>
     <error class='address'>
       <condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
         <item-not-found>
           <no-such-list xmlns='jabber:iq:privacy:error'/>
         </item-not-found>
       </condition>
     </error>
   </iq>

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








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   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 <list/> child element possessing a 'name'
   attribute whose value is set to the list name the user would like to
   edit. The <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").

   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>

   Note: The value of the 'order' attribute for any given item is not
   fixed. Thus in the foregoing example if the user would like to add 4
   items between the "tybalt@capulet.com" item and the
   "paris@shakespeare.lit" item, the user's client can simply renumber
   all the items before submitting the list to the server.

   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 Adding a New Privacy List




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   The same protocol used to edit an existing list is used to create a
   new list. If the list name matches that of an existing list, the
   request to add a new list will overwrite the old one.

8.8 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 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 "conflict" stanza error to the user, which
   SHOULD include a <cannot-remove-list/> child element scoped by the
   'jabber:iq:privacy:error' namespace. The user must first set another
   list to active or default before removing it.

   If the user attempts to remove a list but a list by that name does
   not exist, the server MUST return an "item not found" stanza error to
   the user, which SHOULD include a <no-such-list/> child element scoped
   by the 'jabber:iq:privacy:error' namespace.

   If the user attempts to remove more than one list in the same
   request, the server MUST return a "bad request" stanza error to the
   user, which SHOULD include a <too-many-lists/> child element scoped
   by the 'jabber:iq:privacy:error' namespace.

8.9 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 protocol.





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   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'
               action='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' action='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='msg3'>
     <query xmlns='jabber:iq:privacy'>
       <list name='message-sub-example'>
         <item type='subscription' value='none' action='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.




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   User blocks globally:

   <iq type='set' id='msg4'>
     <query xmlns='jabber:iq:privacy'>
       <list name='message-global-example'>
         <item action='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.

8.10 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 protocol.

   Note: presence notifications do not include presence subscriptions,
   only presence information that is broadcasted to the user because the
   user previously subscribed to a contact's presence information. Thus
   this includes presence stanzas with no 'type' attribute or of
   type='unavailable' only.

   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'
               action='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.







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   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' action='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='to' action='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 action='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.





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8.11 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 protocol.

   Note: presence notifications do not include presence subscriptions,
   only presence information that is broadcasted to contacts because
   those contacts previously subscribed to the user's presence
   information. Thus this includes presence stanzas with no 'type'
   attribute or of type='unavailable' only. Note also that because
   information about last activity MAY be requested by a contact (as
   defined in Section 4.4), a user SHOULD block both outbound presence
   and IQs in relation to any given entity.

   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'
               action='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' action='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.



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   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='from'
               action='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 action='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.

8.12 Blocking IQs

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













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   User blocks based on JID:

   <iq type='set' id='iq1'>
     <query xmlns='jabber:iq:privacy'>
       <list name='iq-jid-example'>
         <item type='jid' value='tybalt@capulet.com'
               action='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 of type "get" or "set" from the user
   with the specified JID.

   User blocks based on roster group:

   <iq type='set' id='iq2'>
     <query xmlns='jabber:iq:privacy'>
       <list name='iq-group-example'>
         <item type='group' value='Enemies' action='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 of type "get" or "set" from any users in
   the specified roster group.

   User blocks based on subscription type:

   <iq type='set' id='iq3'>
     <query xmlns='jabber:iq:privacy'>
       <list name='iq-sub-example'>
         <item type='subscription' value='none'
               action='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 of type "get" or "set" from any users



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   with the specified subscription type.

   User blocks globally:

   <iq type='set' id='iq4'>
     <query xmlns='jabber:iq:privacy'>
       <list name='iq-global-example'>
         <item action='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 of type "get" or "set" from any other
   users.

8.13 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 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'
               action='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.












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   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' action='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'
               action='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 action='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.

8.14 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.



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   If a blocked entity attempts to send an IQ stanza of type "get" or
   "set" to the user, the user's server MUST return to the sending
   entity a <feature-not-implemented/> error of class "recipient" in the
   'urn:ietf:params:xml:ns:xmpp-stanzas' namespace, 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:last'/>
   </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:last'/>
     <error class='recipient'>
       <condition xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'>
         <feature-not-implemented/>
       </condition>
     </error>
   </iq>


8.15 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
      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



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      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:

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































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9. Server Rules for Handling XML Stanzas

   Each server implementation will contain its own "delivery tree" for
   handling stanzas it receives. Such a tree determines whether a stanza
   needs to be routed to another domain, processed internally, or
   delivered to a connected resource associated with a registered user.
   The following rules apply:

9.1 No 'to' Address

   If the stanza possesses no 'to' attribute, the server SHOULD process
   it on behalf of the entity that sent it. Because all stanzas received
   from other servers MUST possess a 'to' attribute, this rule applies
   only to stanzas received from an entity (usually a client) that is
   connected to the server. If the server receives a presence stanza
   with no 'to' attribute, the server MUST broadcast it to the entities
   that are subscribed to a user's presence. If the server receives an
   IQ stanza of type "get" or "set" with no 'to' attribute and it
   understands the namespace that scopes the content of the stanza, it
   MUST process the stanza on behalf of the user who sent the stanza
   (where the meaning of "process" is determined by the semantics of the
   scoping namespace).

9.2 Foreign Domain

   If the hostname of the domain identifier portion of the JID contained
   in the 'to' attribute does not match the hostname of the server
   itself or a subdomain thereof, the server SHOULD route the stanza to
   the foreign domain (subject to local service provisioning and
   security policies regarding inter-domain communication). If routing
   to the recipient's server is unsuccessful, the sender's server MUST
   return 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 MUST return an error to the
   sender by way of the sender's server.

9.3 Subdomain

   If the hostname of the domain identifier portion of the JID contained
   in the 'to' attribute matches a subdomain of the server itself, the
   server MAY process the stanza itself or MAY route the stanza to a
   specialized service that is responsible for that subdomain (if any).

9.4 Bare Domain or Specific Resource

   If the hostname of the domain identifier portion of the JID contained
   in the 'to' attribute matches the hostname of the server itself and
   the JID contained in the 'to' attribute is of the form <domain> or



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   <domain/resource>, the server SHOULD process the stanza as
   appropriate for the stanza type; if the stanza is an IQ stanza and
   the server understands the namespace that scopes the content of the
   stanza, the server SHOULD process the request according to the
   semantics of the scoping namespace, and MUST reply with an IQ of type
   "result" or "error".

9.5 User in Same Domain

   If the hostname of the domain identifier portion of the JID contained
   in the 'to' attribute matches the hostname of the server itself and
   the JID contained in the 'to' attribute is of the form <user@domain>
   or <user@domain/resource>, the server SHOULD first apply any privacy
   rules (Section 8) that are in force. If privacy rules allow the
   stanza, it SHOULD be routed or delivered to the intended recipient of
   the stanza as represented by the JID contained in the 'to' attribute.
   The following rules apply:

   1.  If the JID contains a resource identifier (i.e., is of the form
       <user@domain/resource>) and there is a connected resource whose
       authzid matches the full JID, the recipient's server MUST deliver
       the stanza to the session that exactly matches the resource
       identifier.

   2.  If the JID contains a resource identifier and there is no
       connected resource whose authzid matches the full JID, the
       recipient's server SHOULD return to the sender a
       <recipient-unavailable/> error of class "recipient" in the
       'urn:ietf:params:xml:ns:xmpp-stanzas' namespace.

   3.  If the JID contains only a user@domain and there is at least one
       connected resource available for the user, the recipient's server
       MUST follow these rules:

       1.  For message stanzas, the server SHOULD deliver the stanza to
           the connected resource that provided the highest value for
           the <priority/> element; if two resources have the same
           priority, the server MAY use some other rule (e.g., most
           recent connect time or activity time) to choose between them;
           however, the server MUST NOT deliver the stanza to a
           connected resource that provided a negative value for the
           <priority/> element.

       2.  For presence stanzas other than those of type "probe", the
           server MUST deliver the stanza to all connected resources,
           except that the server MUST NOT deliver the stanza to a
           connected resource that provided a negative value for the
           <priority/> element; for presence probes, the server SHOULD



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           reply based on the rules defined in Section 4.1.

       3.  For IQ stanzas, the server SHOULD deliver the stanza to all
           connected resources, except that the server MUST NOT deliver
           the stanza to a connected resource that provided a negative
           value for the <priority/> element.

   4.  If the JID contains only a user@domain and there are no connected
       resource associated with the user (e.g., an IM user is offline),
       the server MAY choose to store message stanzas and presence
       subscription requests on behalf of the user and deliver the
       stanza when an entity next becomes available for that user. If
       offline storage is not enabled, the server MUST return to the
       sender a <service-unavailable/> error of class "server" in the
       'urn:ietf:params:xml:ns:xmpp-stanzas' namespace. (Note well that
       offline storage is not defined in XMPP since it strictly is a
       matter of implementation and service provisioning.)


































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10. IANA Considerations

10.1 XML Namespace Name for Session Data

   A URN sub-namespace for session-related data in the Extensible
   Messaging and Presence Protocol (XMPP) is defined as follows.

   URI: urn:ietf:params:xml:ns:xmpp-session

   Specification: [RFCXXXX]

   Description: This is the XML namespace name for session-related data
      in the Extensible Messaging and Presence Protocol (XMPP) as
      defined by [RFCXXXX].

   Registrant Contact: IETF, XMPP Working Group, <xmppwg@jabber.org>



































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11. Security Considerations

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















































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Normative References

   [1]  Saint-Andre, P. and J. Miller, "XMPP Core
        (draft-ietf-xmpp-core-12, work in progress)", May 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]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.








































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Informative References

   [4]  Jabber Software Foundation, "Jabber Software Foundation", August
        2001, <http://www.jabber.org/>.

   [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

   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. Documentation of
   this protocol is maintained by the Jabber Software Foundation [4] at
   <http://www.jabber.org/protocol/>.










































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Appendix B. XML Schemas

   The following XML schemas are descriptive, not normative.

B.1 session

   <?xml version='1.0' encoding='UTF-8'?>
   <xs:schema
       xmlns:xs='http://www.w3.org/2001/XMLSchema'
       targetNamespace='urn:ietf:params:xml:ns:xmpp-session'
       xmlns='urn:ietf:params:xml:ns:xmpp-session'
       elementFormDefault='qualified'>

     <xs:element name='session'/>

   </xs:schema>


B.2 jabber:iq:last

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

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

   </xs:schema>


B.3 jabber:iq:privacy

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

     <xs:element name='query'>
       <xs:complexType>



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         <xs:sequence>
           <xs:element ref='active' minOccurs='0' maxOccurs='1'/>
           <xs:element ref='default' minOccurs='0' maxOccurs='1'/>
           <xs:element ref='list' minOccurs='0' maxOccurs='unbounded'/>
         </xs:sequence>
       </xs:complexType>
     </xs:element>

     <xs:element name='active'>
       <xs:complexType>
         <xs:attribute name='name' type='xs:string' use='optional'/>
       </xs:complexType>
     </xs:element>

     <xs:element name='default'>
       <xs:complexType>
         <xs:attribute name='name' type='xs:string' use='optional'/>
       </xs:complexType>
     </xs:element>

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

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



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               <xs:enumeration value='group'/>
               <xs:enumeration value='jid'/>
               <xs:enumeration value='subscription'/>
             </xs:restriction>
           </xs:simpleType>
         </xs:attribute>
         <xs:attribute name='value' type='xs:string' use='optional'/>
       </xs:complexType>
     </xs:element>

     <xs:element name='iq'/>
     <xs:element name='message'/>
     <xs:element name='presence-in'/>
     <xs:element name='presence-out'/>

   </xs:schema>


B.4 jabber:iq:privacy:error

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

     <xs:element name='cannot-remove-list'/>
     <xs:element name='no-such-list'/>
     <xs:element name='too-many-lists'/>

   </xs:schema>


B.5 jabber:iq:roster

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

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



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

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

   </xs:schema>






















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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-10

   o  Clarified presence responsibilities for servers and clients.

   o  Clarified the routing and delivery rules for servers.

   o  Made the xml:lang examples more complete.

   o  Corrected several errors in the unsubscribe workflow.

   o  Made small editorial changes in several sections.


C.2 Changes from draft-ietf-xmpp-im-09

   o  Clarified rules regarding allowable JID types in rosters.

   o  Further clarified the semantics and routing implications of
      presence priorities.

   o  Removed several obsolete subsections.


C.3 Changes from draft-ietf-xmpp-im-08

   o  Removed authorization content (now addressed in XMPP Core).

   o  Added protocol for initiating an IM session, including schema and
      IANA registration template.

   o  Corrected <*-condition/> elements to be <condition/>.

   o  Made small editorial changes to address RFC Editor requirements.


C.4 Changes from draft-ietf-xmpp-im-07

   o  Added several error cases for resource authorization and updated
      relevant schema.







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C.5 Changes from draft-ietf-xmpp-im-06

   o  Specified that IQ result stanzas are required in response to
      roster pushes.

   o  Changed stanza error namespace names to conform to the format
      defined in "The IETF XML Registry" as specified in XMPP Core.

   o  Removed note to RFC Editor regarding provisional namespace names.


C.6 Changes from draft-ietf-xmpp-im-05

   o  Removed use of ask='unsubscribe' per list discussion.

   o  Clarified handling of resource conflict during authorization.

   o  Added schemas for jabber:iq:auth, jabber:iq:auth:error, and
      jabber:iq:privacy:error.

   o  Corrected several small protocol errors in the examples.

   o  Clarified semantics of message types.


C.7 Changes from draft-ietf-xmpp-im-04

   o  Specified sending of unavailable presence after unsubscribe and
      subscription-cancellation actions.

   o  Further specified syntax and business rules for privacy lists.

   o  Brought error codes into line with definitions in
      draft-ietf-xmpp-core.

   o  Added note to RFC Editor regarding provisional namespace names.

   o  Removed vCard content and DTD, instead pointing to JSF
      documentation.


C.8 Changes from draft-ietf-xmpp-im-03

   o  Fixed order processing on privacy rules per list discussion.

   o  Made numerous small editorial changes.





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C.9 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.10 Changes from draft-ietf-xmpp-im-01

   o  Made numerous small editorial changes.


C.11 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.12 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
      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.




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

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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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