TOC 
Network Working GroupJ. Miller
Internet-DraftP. Saint-Andre
Expires: December 20, 2002Jabber Software Foundation
 June 21, 2002

XMPP Instant Messaging
draft-miller-xmpp-im-00

Status of this Memo

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

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

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

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

This Internet-Draft will expire on December 20, 2002.

Copyright Notice

Copyright (C) The Internet Society (2002). All Rights Reserved.

Abstract

This document describes the specific extensions to and applications of the eXtensible Messaging and Presence Protocol (XMPP) that are necessary to create a basic instant messaging and presence application (specificlaly, an application that is compatible with the open-source Jabber instant messaging system).



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Table of Contents




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1. Introduction

1.1 Scope

The core features of the XMPP protocol (XMPP Core[2]) provide the building blocks for many types of near-real-time applications. This document describes the specific extensions to and applications of XMPP Core that are used to create the basic functionality expected of an instant messaging and presence application (specifically, an application that is compatible with the open-source Jabber instant messaging system). Much of this functionality is enabled by the use of extensions that are defined by namespaced elements included within the core data elements defined in XMPP Core.

1.2 Terminology

This document inherits the terminology defined in XMPP Core[2].

1.3 Requirements

For the purposes of this document, we stipulate that a basic instant messaging and presence application needs to enable a node to perform the following functionality:

1.4 Conventions Used in this Document

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[1].

1.5 Discussion Venue

The authors welcome discussion and comments related to the topics presented in this document, preferably on the "jabber-ietf@jabber.org" mailing list (archives and subscription information are available at http://www.jabber.org/cgi-bin/mailman/listinfo/jabber-ietf/).

1.6 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 URI schemes, namespaces, and other protocol syntax. Jabber[tm] is a trademark of Jabber, Inc. If the IETF places this document, or a successor document, on the standards track, then Jabber, Inc. grants permission for use of the trademark "Jabber" in association with that specification.



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2. Registration

Registering with a host is necessary in order for a node to engage in any desired functionality. Certainly such registration MAY (and frequently does) occur outside the context of an instant messaging and presence application. However, XMPP also enables a node to register with a host within the context of an IM system. This functionality is enabled by sending and receiving IQ chunks in a request-response pattern, where the IQ chunks contain <query/> elements in the jabber:iq:register namespace.

2.1 Registration Data Flow

Step 1: Node queries host regarding information that is required in order to register:

<iq type="get" 
    to="capulet.com"
    id="reg_1">
  <query xmlns="jabber:iq:register"/>
</iq>
          

Step 2: Host responds with the required registration fields:

<iq type="result" 
    from="capulet.com" 
    id="reg_1">
  <query xmlns="jabber:iq:register">
    <instructions>
      Choose a username and password to register with this service.
    </instructions>
    <email/>
    <password/>
    <username/>
  </query>
</iq>
          

Note: the node is REQUIRED to provide information for all of the elements (other than <instructions/>) contained in the IQ result. (Note also that the XML chunk shown above does not include a 'to' attribute, since the connected socket does not yet have an account.)

Step 3: Node provides required information:

<iq type="set" 
    to="capulet.com" 
    id="reg_2">
  <query xmlns="jabber:iq:register">
    <email>juliet@capulet.com</email>
    <password>R0m30</password>
    <username>juliet</username>
  </query>
</iq>
          

Step 4: Host informs node of successful registration:

<iq 
    type="result" 
    from="capulet.com" 
    id="reg_2"/>
            

Step 4 (alt): Host informs node of failed registration:

<iq 
    type="error" 
    from="capulet.com" 
    id="reg_2"/>
  <error code="406">Not Acceptable</error>
</iq>
          

2.2 Cancellation Data Flow

The jabber:iq:register namespace also makes it possible for a user to cancel a registration with a host by sending a <remove/> element as shown below.

Step 1: Node sends request to unregister:

<iq type="set" 
    to="capulet.com" 
    id="unreg_1">
  <query xmlns="jabber:iq:register">
    <remove/>
  </query>
</iq>
          

Step 2: Host informs node of successful unregistration:

<iq 
    type="result" 
    from="capulet.com" 
    id="unreg_1"/>
            

2.3 Definition of the jabber:iq:register Namespace

2.3.1 Children

While numerous fields are available for use in the jabber:iq:register namespace, only those fields (other than <instructions/>) sent from the host in an IQ result are REQUIRED in order to register. The officially-recognized fields available for use are as follows:

2.3.2 DTD

<!ELEMENT query ((instructions? | username? | 
    password? | name? | email? | address? | 
    city? | state? | zip? | phone? | url? | 
    date? | misc? | text? | remove?)*)>

<!ELEMENT instructions (#PCDATA)>
<!ELEMENT username (#PCDATA)>
<!ELEMENT password (#PCDATA)>
<!ELEMENT name (#PCDATA)>
<!ELEMENT email (#PCDATA)>
<!ELEMENT address (#PCDATA)>
<!ELEMENT city (#PCDATA)>
<!ELEMENT state (#PCDATA)>
<!ELEMENT zip (#PCDATA)>
<!ELEMENT phone (#PCDATA)>
<!ELEMENT url (#PCDATA)>
<!ELEMENT date (#PCDATA)>
<!ELEMENT misc (#PCDATA)>
<!ELEMENT text (#PCDATA)>
<!ELEMENT remove EMPTY>
          

2.3.3 Schema

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

  <xsd:element name='query'>
    <xsd:complexType>
      <xsd:choice minOccurs='0' maxOccurs='unbounded'>
        <xsd:element ref='instructions'/>
        <xsd:element ref='username'/>
        <xsd:element ref='password'/>
        <xsd:element ref='name'/>
        <xsd:element ref='email'/>
        <xsd:element ref='address'/>
        <xsd:element ref='city'/>
        <xsd:element ref='state'/>
        <xsd:element ref='zip'/>
        <xsd:element ref='phone'/>
        <xsd:element ref='url'/>
        <xsd:element ref='date'/>
        <xsd:element ref='misc'/>
        <xsd:element ref='text'/>
        <xsd:element ref='remove'/>
      </xsd:choice>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name='instructions' type='xsd:string'/>
  <xsd:element name='username' type='xsd:string'/>
  <xsd:element name='password' type='xsd:string'/>
  <xsd:element name='name' type='xsd:string'/>
  <xsd:element name='email' type='xsd:string'/>
  <xsd:element name='address' type='xsd:string'/>
  <xsd:element name='city' type='xsd:string'/>
  <xsd:element name='state' type='xsd:string'/>
  <xsd:element name='zip' type='xsd:string'/>
  <xsd:element name='phone' type='xsd:string'/>
  <xsd:element name='url' type='xsd:string'/>
  <xsd:element name='date' type='xsd:string'/>
  <xsd:element name='misc' type='xsd:string'/>
  <xsd:element name='text' type='xsd:string'/>
  <xsd:element name='remove'/>

</xsd:schema>
          


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3. Authentication

In order to gain access to the network of XMPP-compliant applications and thus engage in standard IM functionality such as exchanging messages and presence, a node must authenticate with a host. The preferred authentication method is SASL. Authentication using the older jabber:iq:auth method is OPTIONAL and MAY be used if a node does not support SASL.

3.1 Authentication Using SASL

If a node is capable of authenticating with SASL, it MUST include the agreed-upon SASL namespace within the opening <stream:stream/> element with which it initiated communications with the host.

For the protocol describing how a node authenticates with a host, refer to XMPP Core[2].

Once a node has authenticated its streams with a host, it MUST provide a resource associated with the connection. This is accomplished by means of the jabber:iq:auth namespace. The protocol for doing so is described below.

Step 1: Node queries host regarding information that is still required to begin a session:

<iq type="get" id="auth_1">
  <query xmlns="jabber:iq:auth">
    <username>juliet</username>
  </query>
</iq>
        

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

<iq type="result" id="auth_1">
  <query xmlns="jabber:iq:auth">
    <username>juliet</username>
    <resource/>
  </query>
</iq>
        

Step 3: Node sends resource information:

<iq type="set" id="auth_2">
  <query xmlns="jabber:iq:auth">
    <username>juliet</username>
    <resource>balcony</resource>
  </query>
</iq>
        

Step 4: Host informs node of successful session initiation:

<iq type="result" id="auth_2"/>
        

3.2 Authentication Using jabber:iq:auth

Earlier iterations of XMPP contained a client-server authentication protocol that was enforced after the stream was negotiated; this protocol, which uses the jabber:iq:auth namespace, is described for completeness in this section.

The jabber:iq:auth namespace provides two things: (1) a simple way for a node to authenticate with a host and (2) a way to create a resource representing a specific connection or session associated with the node.

The following is the data flow for a complete example of a node authenticating with a host.

Step 1: Node queries host regarding information that is required in order to authenticate:

<iq type="get" id="auth_1">
  <query xmlns="jabber:iq:auth">
    <username>juliet</username>
  </query>
</iq>
        

Step 2: Host responds with the required authentication fields:

<iq type="result" id="auth_1">
  <query xmlns="jabber:iq:auth">
    <username>juliet</username>
    <digest/>
    <resource/>
  </query>
</iq>
        

Step 3: Node sends authentication information (encrypted password):

<iq type="set" id="auth_2">
  <query xmlns="jabber:iq:auth">
    <username>juliet</username>
    <digest>64d60e40febe09264c52bc9cbddd5dd1147fae97</digest>
    <resource>balcony</resource>
  </query>
</iq>
        

Step 4: Host informs node of successful authentication:

<iq type="result" id="auth_2"/>
        

Step 4 (alt): Host informs node of failed authentication:

<iq 
    type="error" 
    from="capulet.com" 
    id="auth_2"/>
  <error code="401">Unauthorized</error>
</iq>
        

3.3 Definition of the jabber:iq:auth Namespace

3.3.1 Children

3.3.2 DTD

<!ELEMENT query ((username? | (password | digest)? | resource)*)>

<!ELEMENT username (#PCDATA)>
<!ELEMENT password (#PCDATA)>
<!ELEMENT digest (#PCDATA)>
<!ELEMENT resource (#PCDATA)>
          

3.3.3 Schema

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

  <xsd:element name='query'>
    <xsd:complexType>
      <xsd:choice minOccurs='0' maxOccurs='unbounded'>
        <xsd:element ref='username'/>
        <xsd:choice minOccurs='0' maxOccurs='1'>
          <xsd:element ref='password'/>
          <xsd:element ref='digest'/>
        </xsd:choice>
        <xsd:element ref='resource'/>
      </xsd:choice>
    </xsd:complexType>
  </xsd:element>

  <xsd:element name='username' type='xsd:string'/>
  <xsd:element name='password' type='xsd:string'/>
  <xsd:element name='digest' type='xsd:string'/>
  <xsd:element name='resource' type='xsd:string'/>

</xsd:schema>
          


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4. Exchanging Messages

Exchanging messages is simple within XMPP: using the <message/> data element, a node can send a message to any other node (or, more generally, any entity).

4.1 Specifying an Intended Recipient

A node MAY specify an intended recipient for the message by providing an appropriate JID in the 'to' attribute of the <message/> element. Normally, the value of the 'to' attribute specifies an entity other than the sending node (for exceptions, see the next paragraph). The intended recipient MAY be any valid JID (e.g., a node on the same host, a node on a different host, the host itself, or another host).

If no 'to' address is specified, it is implied that the message is addressed to the sending node itself (i.e., the node@host sending the chunk); furthermore, a message explicitly or implicitly addressed to the sending node itself is processed by the host on behalf of that node. A message addressed to a specific connected resource associated with the sending node is delivered to that node@host/resource (which MAY be different from the connected resource that generated the message).

4.2 Specifying the Sender

A node MAY specify the sender's address by including a 'from' attribute in the message chunk, and MAY specify any resource or full JID in that 'from' attribute. However, a host MUST verify that the value of the 'from' attribute matches the node@host/resource of the connected resource that generated the message chunk. If no 'from' attribute is included, the host MUST add the valid and authenticated from address of the connected resource sending the chunk (i.e., the node@host/resource).

4.3 Specifying a Message Type

As mentioned in XMPP Core[2], 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 node 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 is set or if the type is set to a value other than those specified here, the value SHOULD be defaulted to "normal" by the host. If included, the 'type' attribute SHOULD have one of the following values:

4.4 Specifying a Message Subject

A message chunk MAY contain a child element specifying the subject of the message. The subject MAY NOT contain mixed content.

A message with a subject:

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

4.5 Specifying a Message Thread

A message chunk MAY contain a child element specifying the thread of the message for the purpose of tracking a conversation thread. The content of the <thread/> element is a random string that is generated by the sender; this string MAY be copied back to the sender in subsequent replies. If included, the <thread/> element MUST have no attributes and MAY NOT contain mixed content.

A simple 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>283461923759234</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>283461923759234</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>283461923759234</thread>
</message>
        

4.6 Specifying a Message Body

A message chunk MAY (and usually will) contain a child element specifying the body of the message. The body MAY NOT contain mixed content. If it is necessary to provide the message body in an alternate form (e.g., encrypted using the public key infrastructure or formatted using XHTML), the alternate form SHOULD be contained in an appropriately-namespaced child of the <message/> element other than the <body/> element.

4.7 Specifying Additional Information

A <message/> element MAY house an element containing content that extends the meaning of the message (e.g., an encrypted form of the message body). In common usage this child element is often the <x/> element but MAY be any element. The child element must possess an 'xmlns' namespace declaration (other than those defined for XML streams) that defines all elements contained within the child element.

4.8 Message-Related Errors

If a message sent by a sender cannot be delivered, a host SHOULD return that message to the sender in a message of type "error" along with an appropriate error message (for a list of error messages, see XMPP Core[2]).

A message-related error:

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

<message
    to="juliet@capulet.com"
    from="romeo@montague.net"
    type="error">
  <body>Sleep dwell upon thine eyes</body>
  <error code="404">Not Found</error>
</message>
        


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5. Exchanging Presence Information

Exchanging presence information is made relatively simple within XMPP by using the <presence/> data element. However, we see here a contrast to the handling of messages: although a node MAY send directed presence information to another entity, in general presence information is sent from a node to a host and then broadcasted by the host to any entities that are subscribed to the presence of the sending entity.

5.1 Node and Host Responsibilities

When a node connects to a host, it sends an initial <presence/> element to the host to express default availability.

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

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

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

5.2 Sending Initial Presence

Upon authenticating, a node SHOULD send initial presence to its host indicating that the connected resource is available for communications.

Initial presence sent from node to host:

<presence/>
        

5.3 Specifying Availability Status

A node MAY provide further information about its availability status by using the <show/> element. The recognized values for the show element are "away", "chat", "xa", and "dnd".

Availability status:

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

5.4 Specifying Detailed Status Information

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

Detailed status information:

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

5.5 Probing for Presence

A node or a host MAY probe for the current presence of another entity. A node probing for the presence of another node MUST have permission to view the presence of the probed node.

Presence probe:

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

5.6 Sending Final Presence

Upon ending its session with a host, a node SHOULD send a final presence chunk that is explicitly of type unavailable.

Sending final presence to express unavailable state:

<presence type="unavailable"/>
        


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6. Managing Subscriptions

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

6.1 Requesting a Subscription

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

Sending a subscription request:

<presence 
    to="juliet@capulet.com" 
    from="romeo@montague.net" 
    type="subscribe"/>
        

6.2 Handling a Subscription Request

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

Accepting a subscription request:

<presence 
    to="romeo@montague.net" 
    from="juliet@capulet.com" 
    type="subscribed"/>
        

Denying a presence subscription request:

<presence 
    to="romeo@montague.net" 
    from="juliet@capulet.com" 
    type="unsubscribed"/>
        

6.3 Cancelling a Subscription from Another Entity

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

Cancelling a previously granted subscription request:

<presence 
    to="romeo@montague.net" 
    from="juliet@capulet.com" 
    type="unsubscribed"/>
        

6.4 Unsubscribing from Another Entity's Presence

If a node would like to unsubscribe from the presence of another entity, it sends a presence chunk of type="unsubscribe".

Unsubscribing from an entity's presence:

<presence 
    to="juliet@capulet.com" 
    from="romeo@montague.net" 
    type="unsubscribe"/>
        


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7. Managing One's Roster

One's list of contacts is called a roster. A roster is stored by the host so that a user may access roster information from any connected resource.

7.1 Receiving One's Roster on Login

Upon connecting to the host, a node SHOULD request the roster (however, because receiving the roster may not be desirable for all resources, e.g., a connection with limited bandwidth, the node's request for the roster is OPTIONAL).

Node requests current roster from host:

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

Node receives roster from the host:

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

7.2 Adding a Roster Item

At any time, a node MAY add an item to its roster.

Node 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>
</iq>
        

The host is responsible for updating the roster information in persistent storage, and also for pushing that change out to all connected resources for the node using an iq element of type "set". This enables all connected resources to remain in sync with the host-based roster information.

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

<iq type="result" id="roster_2"/>
<iq type="set" id="roster_3" to="juliet@capulet.com/balcony"/>
  <query xmlns="jabber:iq:roster">  
    <item 
        name="Nurse" 
        jid="nurse@capulet.com">
      <group>Servants</group>
    </item>
</iq>
<iq type="set" id="roster_3" to="juliet@capulet.com/chamber"/>
  <query xmlns="jabber:iq:roster">  
    <item 
        name="Nurse" 
        jid="nurse@capulet.com"
        subscription="none">
      <group>Servants</group>
    </item>
</iq>
        

7.3 Deleting a Roster Item

At any time, a node MAY delete an item from its roster.

Node adds a new item:

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

Note: as with adding a roster item, when deleting a roster item the host is responsible for updating the roster information in persistent storage, and also for pushing that change out to all connected resources for the node using an iq element of type "set".

7.4 Definition of the jabber:iq:roster Namespace

7.4.1 Children

A <query/> element scoped by the jabber:iq:roster namespace MAY contain zero or more <item/> elements. An item element MAY contain the following attributes:

An <item/> element MAY contain zero or more instances of the following element:

7.4.2 DTD

<!ELEMENT query ((item)*)>

<!ELEMENT item ((group)*)>
<!ATTLIST item
    jid CDATA #REQUIRED
    name CDATA #IMPLIED
    subscription ( to | from | both | none | remove ) #IMPLIED
    ask ( subscribe | unsubscribe ) #IMPLIED
    >
<!ELEMENT group (#PCDATA)>
          

7.4.3 Schema

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

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

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

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

</xsd:schema>
          


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8. Routing and Delivery Guidelines

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



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9. Security Considerations

For general security considerations, refer to the relevant section of XMPP Core[2].

9.1 Secure Identity and Encryption

Nodes MAY optionally support signing and encrypting messages and presence by using the Public Key Infrastructure (e.g., PGP/GnuPG), with the encrypted or signed data sent in an <x/> element within the jabber:x:encrypted or jabber:x:signed namespace. (These are informational protocols approved by the Jabber Software Foundation and are not covered in this document.)

Implementations MAY choose to offer MIME-based security services providing message integrity and confidentiality, such as OpenPGP[4] or S/MIME[5].

9.2 Node Connections

The IP address and method of access of nodes MUST never be made available by a host, nor are any connections other than the original host connection required. This helps protect the node's host from direct attack or identification by third parties.



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References

[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[2] Miller, J. and P. Saint-Andre, "XMPP Core (draft-miller-jabber-xmpp-core-00, work in progress)", June 2002.
[3] World Wide Web Consortium, "Secure Hash Algorithm - Version 1.0", October 1997.
[4] Elkins, M., Del Torto, D., Levien, R. and T. Roessler, "MIME Security with OpenPGP", RFC 3156, August 2001.
[5] Ramsdell, B., "S/MIME Version 3 Message Specification", RFC 2633, June 1999.
[6] Freier, A., Karlton, P. and P. Kocher, "The SSL Protocol - Version 3.0", November 1996.
[7] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence and Instant Messaging", RFC 2778, February 2000.
[8] Day, M., Aggarwal, S., Mohr, G. and J. Vincent, "A Model for Presence and Instant Messaging", RFC 2779, February 2000.


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Authors' Addresses

  Jeremie Miller
  Jabber Software Foundation
  1899 Wynkoop Street, Suite 600
  Denver, CO 80202
  US
EMail:  jeremie@jabber.org
URI:  http://www.jabber.org/
  
  Peter Saint-Andre
  Jabber Software Foundation
  1899 Wynkoop Street, Suite 600
  Denver, CO 80202
  US
EMail:  stpeter@jabber.org
URI:  http://www.jabber.org/


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Full Copyright Statement

Acknowledgement