Network Working Group P. Saint-Andre
Internet-Draft Jabber Software Foundation
Expires: October 10, 2004 April 11, 2004
XMPP URI Format
draft-saintandre-xmpp-uri-03
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Copyright Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This document defines a URI scheme for use in addressing entities
that can communicate via the Extensible Messaging and Presence
Protocol (XMPP).
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Discussion Venue . . . . . . . . . . . . . . . . . . . . . . . 3
2. Narrative . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1 Rationale . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 Query Component . . . . . . . . . . . . . . . . . . . . . . . 4
3. xmpp: URI IANA Registration . . . . . . . . . . . . . . . . . 6
3.1 URI scheme name . . . . . . . . . . . . . . . . . . . . . . . 6
3.2 URI scheme syntax . . . . . . . . . . . . . . . . . . . . . . 6
3.3 Character encoding considerations . . . . . . . . . . . . . . 6
3.4 Intended usage . . . . . . . . . . . . . . . . . . . . . . . . 6
3.5 Security considerations . . . . . . . . . . . . . . . . . . . 6
3.6 Relevant publications . . . . . . . . . . . . . . . . . . . . 6
3.7 Person and email address to contact for further information . 6
3.8 Author/change controller . . . . . . . . . . . . . . . . . . . 7
3.9 Applications and/or protocols which use this URI scheme
name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
Normative References . . . . . . . . . . . . . . . . . . . . . 7
Informative References . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 8
A. Revision History . . . . . . . . . . . . . . . . . . . . . . . 8
A.1 Changes from draft-saintandre-xmpp-uri-02 . . . . . . . . . . 8
A.2 Changes from draft-saintandre-xmpp-uri-01 . . . . . . . . . . 9
A.3 Changes from draft-saintandre-xmpp-uri-00 . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . 10
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1. Introduction
The Extensible Messaging and Presence Protocol (XMPP) [XMPP-CORE]
specifies that within the context of the streaming XML technology
that forms the foundation of XMPP, the addresses of XMPP entities are
not to be prepended with a URI scheme (as defined in RFC 2396 [URI]).
However, many applications external to the existing network would
like to address XMPP entities as full URIs; examples are databases
that need to store XMPP addresses as URIs and non-native user agents
(such as web browsers) that provide an interface to XMPP services.
This memo defines an xmpp: URI scheme for use by such applications,
and conforms to both the requirements in Registration Procedures for
URL Scheme Names [URL-REG] and the recommendations in Guidelines for
new URL Schemes [URL-GUIDE].
1.1 Terminology
This document inherits terminology described in [XMPP-CORE].
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 [TERMS].
1.2 Discussion Venue
The author welcomes 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/>.
2. Narrative
2.1 Rationale
Many types of application can be built using XMPP. The best-known
such application is instant messaging (IM) and presence (as described
in [IMP-MODEL] and [IMP-REQS] and defined for XMPP in [XMPP-IM]).
Therefore it might seem appropriate to use the im: and pres: URI
schemes specified by Common Profile for Instant Messaging (CPIM)
[CPIM] and Common Profile for Presence (CPP) [CPP], rather than to
define an XMPP-specific URI scheme. However, while the im: and pres:
URI schemes are appropriate for instant messaging and presence
applications and are therefore mentioned normatively in [XMPP-IM],
they are not necessarily appropriate for all XMPP applications.
Because XMPP is fundamentally an XML streaming technology rather than
an instant messaging and presence technology per se, XMPP
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applications may conform to [XMPP-CORE] but not [XMPP-IM] and thus
not implement instant messaging and presence semantics. Indeed, XMPP
is already used in applications such as network management, workflow
applications, generic publish-subscribe, remote procedure calls,
content syndication, gaming, and middleware. These applications
require an addressing scheme that is not tied to the particular
semantics of the im: and pres: URI schemes. Therefore, this document
defines a generic URI scheme that will enable applications to address
as a URI any entity that can communicate via XMPP.
Note well that on an XMPP network, entities are to be addressed as
<[node@]domain[/resource]> (i.e., without a URI scheme) rather than
as <xmpp:[node@]domain[/resource]>. The xmpp: URI format is provided
for the sake of non-native interfaces and applications only; native
applications are strongly encouraged not to prepend XMPP addresses
with the xmpp: URI scheme when addressing XML stanzas sent over an
XMPP network.
2.2 Form
The syntax for an xmpp: URI is as follows (where the jid rule is
defined in [XMPP-CORE]).
"xmpp:" jid [ "?" query ]
An xmpp: URI is opaque rather than hierarchical, and thus is similar
to a mailto: URI as specified in RFC 2368 [MAILTO]. Because an xmpp:
URI is opaque, the JID contained therein SHOULD include only a node
identifier (OPTIONAL) and domain identifier (REQUIRED) as defined in
[XMPP-CORE]. An xmpp: URI MAY include the resource identifier
portion of a JID if the XMPP entity must be addressed as such, but
this is not recommended since the delimiter used before a resource
identifier in XMPP addresses is the slash character ("/"), which is
discouraged by [URI] in opaque URIs.
2.3 Query Component
If an xmpp: URI is presented in an end-user application that provides
a non-native interface to an XMPP service (e.g., a web browser),
interacting with such a URI SHOULD trigger the application to present
a user with an appropriate interface to complete an action such as
sending a message or sending presence. In order to specify the
possible actions, two "header" values of the query component are
defined: "presence" and "message". Usage is described below.
2.3.1 Messages
In order to invoke an interface for sending a message, the URI SHOULD
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be of the form <xmpp:user@host?message>.
The query component MAY include parameters that further specify the
message to be sent to the intended recipient. The following
parameters are OPTIONAL for messages, corresponding to the <body/>,
<subject/>, and <thread/> children of the XML <message/> stanza as
defined in [XMPP-IM]:
o body (the natural-language contents of the message)
o subject (the topic of the message)
o thread (for grouping of multiple messages into a common thread)
The following example illustrates the use of these parameters:
Sending a message
xmpp:user@host?message&subject=hi&body=Hello%20World&thread=abc123
2.3.2 Presence
In order to invoke an interface for sending presence information, the
URI SHOULD be of the form <xmpp:user@host?presence>. The intended
scope is the sending of presence notifications about the availability
of the sender, not the management of presence subscriptions (for the
semantic and syntactic differences between presence notifications and
presence subscriptions, see [XMPP-IM]).
The query component MAY include parameters that further specify the
presence information to be sent to the intended recipient. The
following parameters are OPTIONAL for presence, corresponding to the
'type' attribute and the <show/>, <status/>, and <priority/> children
of the <presence/> stanza as defined in [XMPP-IM]:
o type (the only allowable value for presence notifications is
"unavailable"; if the type is not specified, the sender is defined
to be available)
o show (one of "away", "xa", "dnd", or "chat")
o status (a user-defined status message)
o priority (an integer specifying the rough likelihood of receiving
messages at this resource)
The following example illustrates the use of these parameters:
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Sending Presence Information
xmpp:user@host?presence&show=dnd&status=taking%20a%20nap
3. xmpp: URI IANA Registration
This section provides the information required to register the xmpp:
URI scheme.
3.1 URI scheme name
xmpp
3.2 URI scheme syntax
The syntax for an xmpp: URI is defined below using Augmented
Backus-Naur Form as specified by [ABNF]. The jid rule is defined in
[XMPP-CORE].
XMPP-URI = "xmpp:" jid [ "?" query ]
3.3 Character encoding considerations
Representation of non-ASCII character sets in local-part strings is
limited to the standard methods provided as extensions to RFC 2822
[IMF]. Specifically, for each byte, if the byte is not in the set
A-Za-z0-9!$*.?_~+= then transform the byte to %hexhex as described in
Section 2.2.5 of [URL-GUIDE].
3.4 Intended usage
The xmpp: URI is intended to be used by interfaces to an XMPP network
from non-native user agents such as web browsers, as well as by
non-native applications that need to address XMPP entities as full
URIs.
3.5 Security considerations
See Security Considerations (Section 5) of this document.
3.6 Relevant publications
[XMPP-CORE]
3.7 Person and email address to contact for further information
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Peter Saint-Andre [mailto:stpeter@jabber.org]
3.8 Author/change controller
This scheme is registered under the IETF tree. As such, the IETF
maintains change control.
3.9 Applications and/or protocols which use this URI scheme name
Applications (other than native native XMPP applications) that
provide an interface to XMPP services or that need to address XMPP
entities as full URIs.
4. IANA Considerations
This entire document addresses IANA considerations.
5. Security Considerations
Detailed security considerations for XMPP are given in [XMPP-CORE].
Providing an interface to XMPP services from non-native applications
introduces new security concerns. For example, the ability to
interact with XMPP entities via a web browser may expose sensitive
information to attacks that are not possible or that are unlikely on
a native XMPP network. Due care must be taken in deciding what
information is appropriate for representing in xmpp: URIs; in
particular, passwords MUST NOT be represented.
Normative References
[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[IMF] Resnick, P., "Internet Message Format", RFC 2822, April
2001.
[TERMS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[URI] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform
Resource Identifiers (URI): Generic Syntax", RFC 2396,
August 1998, <http://www.ietf.org/rfc/rfc2396.txt>.
[URL-GUIDE]
Masinter, L., Alvestrand, H., Zigmond, D. and R. Petke,
"Guidelines for new URL Schemes", RFC 2718, November 1999.
[URL-REG] Petke, R. and I. King, "Registration Procedures for URL
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Scheme Names", BCP 35, RFC 2717, November 1999.
[XMPP-CORE]
Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", draft-ietf-xmpp-core-22 (work in
progress), January 2004.
[XMPP-IM] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence",
draft-ietf-xmpp-im-21 (work in progress), January 2004.
Informative References
[CPIM] Peterson, J., "Common Profile for Instant Messaging
(CPIM)", draft-ietf-impp-im-04 (work in progress), August
2003.
[CPP] Peterson, J., "Common Profile for Presence (CPP)",
draft-ietf-impp-pres-04 (work in progress), August 2003.
[IMP-MODEL]
Day, M., Rosenberg, J. and H. Sugano, "A Model for
Presence and Instant Messaging", RFC 2778, February 2000.
[IMP-REQS]
Day, M., Aggarwal, S. and J. Vincent, "Instant Messaging /
Presence Protocol Requirements", RFC 2779, February 2000.
[MAILTO] Hoffman, P., Masinter, L. and J. Zawinski, "The mailto URL
scheme", RFC 2368, July 1998.
Author's Address
Peter Saint-Andre
Jabber Software Foundation
EMail: stpeter@jabber.org
Appendix A. Revision History
Note to RFC Editor: please remove this entire appendix, and the
corresponding entries in the table of contents, prior to publication.
A.1 Changes from draft-saintandre-xmpp-uri-02
o Corrected several small textual errors.
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o Clarified the scope of allowable presence information.
A.2 Changes from draft-saintandre-xmpp-uri-01
o Clarified guidelines for escaping of UTF-8 characters.
o Specified usage of query component.
A.3 Changes from draft-saintandre-xmpp-uri-00
o Modified ABNF to track changes to XMPP Core.
o Clarified a few matters in the text.
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