Network Working Group P. Saint-Andre
Internet-Draft Jabber Software Foundation
Expires: June 9, 2005 December 9, 2004
A Uniform Resource Identifier (URI) Scheme for the Extensible
Messaging and Presence Protocol (XMPP)
draft-saintandre-xmpp-uri-08
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Copyright Notice
Copyright (C) The Internet Society (2004).
Abstract
This document defines a Uniform Resource Identifier (URI) scheme for
use in identifying or interacting with 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
2. Description of xmpp: URI Scheme . . . . . . . . . . . . . . . 3
2.1 Rationale . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 Form . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.3 Authority Component . . . . . . . . . . . . . . . . . . . 5
2.4 Path Component . . . . . . . . . . . . . . . . . . . . . . 6
2.5 Query Component . . . . . . . . . . . . . . . . . . . . . 6
2.6 Fragment Identifier Component . . . . . . . . . . . . . . 8
2.7 Generation of XMPP URIs . . . . . . . . . . . . . . . . . 8
2.8 Processing of XMPP URIs . . . . . . . . . . . . . . . . . 11
2.9 Internationalization . . . . . . . . . . . . . . . . . . . 14
3. IANA Registration of xmpp: URI Scheme . . . . . . . . . . . . 14
3.1 URI scheme name . . . . . . . . . . . . . . . . . . . . . 14
3.2 URI scheme syntax . . . . . . . . . . . . . . . . . . . . 14
3.3 Character encoding considerations . . . . . . . . . . . . 15
3.4 Intended usage . . . . . . . . . . . . . . . . . . . . . . 15
3.5 Applications and/or protocols which use this URL
scheme name . . . . . . . . . . . . . . . . . . . . . . . 15
3.6 Security considerations . . . . . . . . . . . . . . . . . 15
3.7 Relevant publications . . . . . . . . . . . . . . . . . . 16
3.8 Person and email address to contact for further
information . . . . . . . . . . . . . . . . . . . . . . . 16
3.9 Author/change controller . . . . . . . . . . . . . . . . . 16
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
5. Security Considerations . . . . . . . . . . . . . . . . . . . 16
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.1 Normative References . . . . . . . . . . . . . . . . . . . . 16
6.2 Informative References . . . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 19
Intellectual Property and Copyright Statements . . . . . . . . 20
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1. Introduction
The Extensible Messaging and Presence Protocol (XMPP) is a streaming
XML technology that enables any two entities on a network to exchange
well-defined but extensible XML elements (called "XML stanzas") in
close to real time. [XMPP-CORE] specifies that on an XMPP network
itself, the address of an XMPP entity MUST NOT be prepended with a
Uniform Resource Identifier (URI) scheme (as defined in [URI]).
However, many applications external to an XMPP network may need to
identify XMPP entities as full URIs; examples include databases that
need to store XMPP addresses and non-native user agents (e.g., web
browsers and calendaring applications) that provide interfaces to
XMPP services. In order to address the needs of such applications,
this memo defines an xmpp: URI scheme that conforms to both the
requirements in [URL-REG] and the recommendations in [URL-GUIDE].
1.1 Terminology
This document inherits terminology described in [URI] and
[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].
2. Description of xmpp: URI Scheme
2.1 Rationale
Many types of application can be built using XMPP. As specified in
[XMPP-IM], instant messaging and presence applications of XMPP MUST
handle the im: and pres: URI schemes specified by [CPIM] and [CPP].
However, it is appropriate to define an XMPP-specific URI scheme for
other applications of XMPP (such as network management, workflow
applications, generic publish-subscribe, remote procedure calls,
content syndication, gaming, and middleware) since these applications
do not necessarily implement instant messaging and presence
semantics. Therefore, this document defines a generic URI scheme
that will enable applications to address as a URI any entity that can
communicate via XMPP.
The xmpp: URI scheme is provided mainly for use by non-native
interfaces and applications, and primarily for the purpose of
identification rather than interaction (on the latter distinction,
see Section 1.2.2 of [URI]). In order to ensure interoperability on
XMPP networks, when data is routed to an XMPP entity (e.g., when an
XMPP address is contained in the 'to' or 'from' attribute of an XML
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stanza) or an XMPP entity is otherwise identified in standard XMPP
protocol elements, the entity MUST be addressed as
<[node@]domain[/resource]> (i.e., without a URI scheme), where the
"node identifier", "domain identifier", and "resource identifier"
portions of an XMPP address conform to the definitions provided in
Section 3 of [XMPP-CORE].
(Note: For historical reasons, the term "resource identifier" is used
in XMPP to refer to the optional portion of an XMPP address that
follows the domain identifier and the "/" separator character (for
details, refer to Section 3.4 of [XMPP-CORE]); this use of the term
"resource identifier" is not to be confused with the meanings of
"resource" and "identifier" provided in Section 1.1 of [URI].)
2.2 Form
As described in [XMPP-CORE], an XMPP address (also known as a "JID")
used natively on an XMPP network is a string of Unicode characters
that (1) conforms to a certain set of [STRINGPREP] profiles and
[IDNA] restrictions, (2) follows a certain set of syntax rules, and
(3) is encoded as [UTF-8]. The form of such an address can be
represented using Augmented Backus-Naur Form ([ABNF]) as:
[ node "@" ] domain [ "/" resource ]
The "node" and "resource" rules rely on distinct profiles of
[STRINGPREP] and the "domain" rule relies on the concept of an
internationalized domain name as described in [IDNA]. However,
because a URI is allowed to contain [US-ASCII] characters only and
certain characters are reserved in URIs (the "reserved" rule defined
in [URI]), an XMPP address must be properly handled when transformed
into an XMPP URI (see Section 2.7 of this memo) and the ABNF syntax
needs to be adjusted in order to accurately capture the form of an
XMPP URI as opposed to a native XMPP address. Furthermore, it is
desirable to take advantage of more advanced aspects of URI syntax
and semantics in XMPP URIs, such as authority components, query
components, and fragment identifier components. Therefore, using the
"fragment", "host", "pct-encoded", "query", "sub-delims", and
"unreserved" rules defined in [URI], the ABNF syntax for an XMPP URI
is defined as follows:
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xmppuri = "xmpp:" hier-xmpp [ "?" querycomp ] [ "#" fragment ]
hier-xmpp = authpath / path-xmpp
authpath = "//" auth-xmpp [ "/" path-xmpp ]
auth-xmpp = nodeid "@" host
path-xmpp = [ nodeid "@" ] host [ "/" resid ]
nodeid = *( unreserved / pct-encoded / nodeallow )
nodeallow = "!" / "$" / "%" / "(" / ")" / "*" / "+" / ","
/ ";" / "=" / "^" / "`" / "{" / "|" / "}"
resid = *( unreserved / pct-encoded / sub-delims )
querycomp = querytype [ *pair ]
querytype = *( ALPHA / DIGIT / '-' / '_' / '.' / ':' )
pair = "&" key "=" value
key = *unreserved
value = *( unreserved / pct-encoded )
(Note: It would have been desirable to re-use the "userinfo" rule
from [URI]; however, this was not possible since the "userinfo" rule
allows characters that conform to the "sub-delims" rule, but the "&"
and "'" characters (which are allowed by the "sub-delims" rule) are
disallowed in XMPP node identifiers by the Nodeprep profile of
[STRINGPREP] as specified in Appendix A of [XMPP-CORE]. Furthermore,
there is no need to refer to punycode in the URI syntax itself, since
any punycode representation would occur only inside an XMPP
application in order to represent internationalized domain names.)
The following is an example of a basic XMPP URI used for purposes of
identifying a node associated with an XMPP server (an IM user is one
type of such a node, but by no means the only type):
xmpp:juliet@example.com
Further descriptions of the various components of an XMPP URI are
provided in the following sections.
2.3 Authority Component
As explained in Section 2.8 of this memo, in the absence of an
authority component the processing application would authenticate as
a configured user at a configured XMPP server. The presence of an
authority component (always preceded by "//") signals the processing
application to authenticate as the node@domain specified in the
authority component, rather than as a configured node@domain. Thus,
the following XMPP URI indicates to authenticate as
"guest@example.com":
xmpp://guest@example.com
Note well that this is quite different from the following XMPP URI,
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which identifies a node "guest@example.com" but does not signal the
processing application to authenticate as that node:
xmpp:guest@example.com
Similarly, using a possible query component of "?message" to trigger
an interface for sending a message, the following XMPP URI signals
the processing application to authenticate as "guest@example.com" and
send a message to "support@example.com":
xmpp://guest@example.com/support@example.com?message
By contrast, the following XMPP URI signals the processing
application to authenticate as its configured default account and
send a message to "support@example.com":
xmpp:support@example.com?message
(Note: It is unlikely that the authority component will be included
in most XMPP URIs; however, the scheme allows for inclusion of the
authority component if appropriate.)
2.4 Path Component
The path component of an XMPP URI identifies an XMPP address or
specifies the XMPP address to which an XML stanza shall be directed
at the end of URI processing.
For example, the following XMPP URI identifies a node associated with
an XMPP server:
xmpp:juliet@example.com
The following XMPP URI identifies a node associated with an XMPP
server along with a particular XMPP resource identifier associated
with that node:
xmpp:juliet@example.com/balcony
Inclusion of a node is optional in XMPP addresses, so that the
following XMPP URI simply identifies an XMPP server:
xmpp:example.com
2.5 Query Component
There are many potential use cases for encapsulating information in
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the query component of an XMPP URI; examples include but are not
limited to:
o Sending an XMPP message stanza.
o Adding a roster item.
o Sending a presence subscription.
o Probing for current presence information.
o Joining an XMPP-based text chat room (see [JEP-0045]).
o Registering with another entity (see [JEP-0077]).
o Triggering a remote procedure call (see [JEP-0009]).
o Providing a SOAP interface (see [JEP-0072]).
o Discovering the identity or capabilities of another entity (see
[JEP-0030]).
o Interacting with publish-subscribe channels (see [JEP-0060]).
Many of these potential use cases are application-specific, and the
full range of such applications cannot be foreseen in advance given
the continued expansion in XMPP development; however, there is
agreement within the Jabber/XMPP developer community that all of the
uses envisioned to date can be encapsulated via a "query type",
optionally supplemented by one or more "key-value" pairs (this is
similar to the "application/x-www-form-urlencoded" MIME type
described in [HTML]).
As an example, an XMPP URI intended to launch an interface for
sending a message to the XMPP entity "juliet@example.com" might be
represented as follows:
xmpp:juliet@example.com?message
Similarly, an XMPP URI intended to launch an interface for sending a
message to the XMPP entity "juliet@example.com" with a particular
subject might be represented as follows:
xmpp:juliet@example.com?message&subject=Hello%20World
If included, the query component MUST first be encoded as a [UTF-8]
string; any [UTF-8] encoded octets MUST then be converted into
US-ASCII characters, making sure to represent any reserved character
(i.e., any character that conforms to the "reserved" rule defined in
[URI]) and any character that is outside the range of the US-ASCII
coded character set as a percent-encoded octet (see Section 2.1 of
[URI]).
If the processing application does not understand query components,
it MUST ignore the query component and treat the URI as consisting
of, for example, <xmpp:juliet@example.com> rather than
<xmpp:juliet@example.com?query>. If the processing application does
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not understand a particular key within the query component, it MUST
ignore that key and its associated value.
In pursuit of interoperability, it may be valuable to maintain a
registry of query types and perhaps even of keys for use in the query
component portion of XMPP URIs. Given that such values will most
likely be specific to particular applications of XMPP rather than
core to XMPP itself, it seems reasonable that such a registry, if
created, would be maintained by the Jabber Registrar function of the
Jabber Software Foundation as described in [JEP-0053], rather than by
the IANA. A proposal for creating such a registry is described in
[JEP-0147].
2.6 Fragment Identifier Component
As stated in Section 3.5 of [URI], "The fragment identifier component
of a URI allows indirect identification of a secondary resource by
reference to a primary resource and additional identifying
information." Because the resource identified by an XMPP URI does
not make available any media type (see [MIME]) and therefore (in the
terminology of [URI]) no representation exists at an XMPP resource,
the semantics of the fragment identifier component in XMPP URIs are
to be "considered unknown and, effectively, unconstrained" (ibid.).
Particular XMPP applications MAY make use of the fragment identifier
component for their own purposes. However, if a processing
application does not understand fragment identifier components or the
syntax of a particular fragment identifier component included in an
XMPP URI, it MUST ignore the fragment identifier component.
If included, the fragment identifier component MUST first be encoded
as a [UTF-8] string; any [UTF-8] encoded octets MUST then be
converted into US-ASCII characters, making sure to represent any
reserved character (i.e., any character that conforms to the
"reserved" rule defined in [URI]) and any character that is outside
the range of the US-ASCII coded character set as a percent-encoded
octet (see Section 2.1 of [URI]).
2.7 Generation of XMPP URIs
2.7.1 URI Generation Method
When generating a conformant XMPP URI from an XMPP address, it is
necessary to use consistent methods for transforming (1) an XMPP
"node identifier" into a string of US-ASCII characters that conforms
to the "nodeid" rule, (2) an XMPP "domain identifier" into a string
of US-ASCII characters that conforms to the "host" rule, and (3) an
XMPP "resource identifier" into a string of US-ASCII characters that
conforms to the "resid" rule; such methods are described below.
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Naturally, if the XMPP address exists in a non-UTF-8 form (e.g.,
having been written on a piece of paper or having been represented
internally in a computer program as UTF-16), it MUST first be
converted to [UTF-8] before the XMPP URI is generated.
In order to transform an XMPP "node identifier" into a string of
US-ASCII characters that conforms to the "nodeid" rule, the node
identifier MUST first be constructed in accordance with the rules
specified in [XMPP-CORE], including application of the Nodeprep
profile of [STRINGPREP] (see Appendix A of [XMPP-CORE]) and encoding
as a [UTF-8] string; any [UTF-8] encoded octets of the XMPP "node
identifier" MUST then be converted into US-ASCII characters, making
sure to represent any reserved character (i.e., any character that
conforms to the "reserved" rule defined in [URI]) and any character
that is outside the range of the US-ASCII coded character set as a
percent-encoded octet (see Section 2.1 of [URI]).
In order to transform an XMPP "domain identifier" into a string of
US-ASCII characters that conforms to the "host" rule, the domain
identifier MUST first be constructed in accordance with the rules
specified in [XMPP-CORE], including application of the [NAMEPREP]
profile of [STRINGPREP] and encoding as a [UTF-8] string; any [UTF-8]
encoded octets of the XMPP "domain identifier" MUST then be converted
into US-ASCII characters, making sure to represent any reserved
character (i.e., any character that conforms to the "reserved" rule
defined in [URI]) and any character that is outside the range of the
US-ASCII coded character set as a percent-encoded octet (see Section
2.1 of [URI]).
In order to transform an XMPP "resource identifier" into a string of
US-ASCII characters that conforms to the "resid" rule, the resource
identifier MUST first be constructed in accordance with the rules
specified in [XMPP-CORE], including application of the Resourceprep
profile of [STRINGPREP] (see Appendix B of [XMPP-CORE]) and encoding
as a [UTF-8] string; any [UTF-8] encoded octets of the XMPP "resource
identifier" MUST then be converted into US-ASCII characters, making
sure to represent any reserved character (i.e., any character that
conforms to the "reserved" rule defined in [URI]) and any character
that is outside the range of the US-ASCII coded character set as a
percent-encoded octet (see Section 2.1 of [URI]).
In order to form an XMPP URI from the foregoing components, the
generating application MUST concatenate:
1. the "xmpp:" scheme
2. optionally (if an authority component is to be included), the
characters "//", an authority component of the form node@domain,
and the character "/"
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3. optionally (if the XMPP address contained an XMPP "node
identifier"), a string of US-ASCII characters that conforms to
the "nodeid" rule, followed by the "@" character
4. a string of US-ASCII characters that conforms to the "host" rule
5. optionally (if the XMPP address contained an XMPP "resource
identifier"), the character "/" and a string of US-ASCII
characters that conforms to the "resid" rule
6. optionally (if a query component is to be included), the "?"
character and query component
7. optionally (if a fragment identifier component is to be
included), the "#" character and fragment identifier component
2.7.2 URI Generation Example
Consider the following XMPP address:
<jiři@čechy.example/v Praze>
(Note: The string "ř" stands for the Unicode character LATIN
SMALL LETTER R WITH CARON and the string "č" stands for the
Unicode character LATIN SMALL LETTER C WITH CARON, following the "XML
Notation" used in [IRI] to represent characters that cannot be
rendered in ASCII-only documents. The '<' and '>' characters are
not part of the address itself, but are provided to set off the
address for legibility. For those who do not read Czech, this
example could be Anglicized as "george@czech-lands.example/In
Prague".)
In accordance with the process specified above, the generating
application would do the following to generate a valid XMPP URI from
this address:
1. First ensure that the XMPP address conforms to the rules
specified in [XMPP-CORE], including application of the relevant
[STRINGPREP] profiles and encoding as a [UTF-8] string.
2. Split the address into an XMPP "node identifier" ("jiři"),
XMPP "domain identifier" ("čechy.example"), and XMPP
"resource identifier" ("v Praze").
3. Transform the XMPP "node identifier" into a string of US-ASCII
characters that conforms to the "nodeid" rule by converting the
[UTF-8] string to US-ASCII, including conversion of the LATIN
SMALL LETTER R WITH CARON character to its percent-encoded
representation "%C5%99"; the result is the string "ji%C5%99i".
4. Transform the XMPP "domain identifier" into a string of US-ASCII
characters that conforms to the "host" rule by converting the
[UTF-8] string to US-ASCII, including conversion of the LATIN
SMALL LETTER C WITH CARON character to its percent-encoded
representation "%C4%8C"; the result is the string
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"%C4%8Cechy.example".
5. Transform the XMPP "resource identifier" into a string of
US-ASCII characters that conforms to the "resid" rule by
converting the [UTF-8] string to US-ASCII, including conversion
of the " " (SP) character to its percent-encoded representation
"%20"; the result is the string "v%20Praze".
6. Concatenate the following:
1. the "xmpp:" scheme
2. a URI "authority component" if included (not shown in this
example)
3. the string of US-ASCII characters that conforms to the
"nodeid" rule, followed by the "@" character
4. the string of US-ASCII characters that conforms to the "host"
rule
5. the "/" character followed by the string of US-ASCII
characters that conforms to the "resid" rule
6. the "?" character followed by a URI "query component" if
appropriate to the application (not shown in this example)
7. the "#" character followed by a URI "fragment identifier
component" if appropriate to the application (not shown in
this example)
The result is this XMPP URI:
<xmpp:ji%C5%99i@%C4%8Cechy.example/v%20Praze>
2.8 Processing of XMPP URIs
2.8.1 URI Processing Method
As with the generation of an XMPP URI from an XMPP address, so also
with the processing of an XMPP URI (including the extraction of an
XMPP address therefrom): it is necessary to use consistent methods;
such methods are described below.
In order to decompose an XMPP URI, a processing application MUST
separate:
1. the "xmpp:" scheme
2. optionally (if the XMPP URI contains an authority component), the
authority component (the string of US-ASCII characters between
the "//" characters and the first "/" character or the end of the
URI)
3. optionally a string of US-ASCII characters that conforms to the
"nodeid" rule (if any), using the "@" character as a separator
4. a string of US-ASCII characters that conforms to the "host" rule
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5. optionally a string of US-ASCII characters that conforms to the
"resid" rule (if any), using the "/" character as a separator
6. optionally the query component (if any), using the "?" character
as a separator
7. optionally the fragment identifier component (if any), using the
"#" character as a separator
In order to reconstruct the XMPP address from the foregoing
components, the processing application MUST:
o Transform the string of US-ASCII characters that conforms to the
"nodeid" rule into an XMPP "node identifier" by converting each
sequence of percent-encoded octets into the appropriate sequence
of reserved or non-US-ASCII octets by (1) decoding percent-encoded
octets into actual octets, (2) interpreting the octets as [UTF-8],
and (3) applying the Nodeprep profile of [STRINGPREP] as specified
in Appendix A of [XMPP-CORE].
o Transform the string of US-ASCII characters that conforms to the
"host" rule into an XMPP "domain identifier" by converting each
sequence of percent-encoded octets into the appropriate sequence
of reserved or non-US-ASCII octets by (1) decoding percent-encoded
octets into actual octets, (2) interpreting the octets as [UTF-8],
and (3) applying the [NAMEPREP] profile of [STRINGPREP].
o Transform the string of US-ASCII characters that conforms to the
"resid" rule into an XMPP "resource identifier" by converting each
sequence of percent-encoded octets into the appropriate sequence
of reserved or non-US-ASCII octets by (1) decoding percent-encoded
octets into actual octets, (2) interpreting the octets as [UTF-8],
and (3) applying the Resourceprep profile of [STRINGPREP] as
specified in Appendix B of [XMPP-CORE].
o Concatenate the following (ensuring that the resulting string is
encoded as [UTF-8]):
1. the XMPP "node identifier" and the "@" character (if a string
of US-ASCII characters that conforms to the "nodeid" rule was
included)
2. the XMPP "domain identifier"
3. the "/" character and XMPP "resource identifier" (if a string
of US-ASCII characters that conforms to the "resid" rule was
included)
At this point, the processing application would either (1) complete
further XMPP handling itself or (2) invoke a helper application to
complete XMPP handling; such XMPP handling would most likely consist
of the following steps:
1. Authenticating either as the user specified in the authority
component or as the configured user at the configured XMPP server
if not already so authenticated.
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2. Optionally determining the nature of the intended recipient
(e.g., via [JEP-0030]).
3. Optionally presenting an appropriate interface to a user based on
the nature of the intended recipient and/or the contents of the
query component.
4. Generating an XMPP stanza that translates any user or application
inputs into their corresponding XMPP equivalents.
5. Sending the XMPP stanza via the authenticated server connection
for delivery to the intended recipient.
Note: It may help implementors to note that the first two steps of
the "further XMPP handling" are similar to HTTP authentication
([HTTP-AUTH]), while the next three steps are similar to the handling
of mailto: URIs ([MAILTO]).
2.8.2 URI Processing Example
Consider the XMPP URI that resulted from the previous example:
<xmpp:ji%C5%99i@%C4%8Cechy.example/v%20Praze>
In accordance with the process specified above, the processing
application would do the following to extract the XMPP address from
this XMPP URI:
1. Split the URI into a string of US-ASCII characters that conforms
to the "nodeid" rule ("ji%C5%99i"), a string of US-ASCII
characters that conforms to the "host" rule
("%C4%8Cechy.example"), and a string of US-ASCII characters that
conforms to the "resid" rule ("v%20Praze").
2. Transform the string of US-ASCII characters that conforms to the
"nodeid" rule into an XMPP "node identifier" by converting the
percent-encoded representation "%C5%99" to its equivalent [UTF-8]
character (LATIN SMALL LETTER R WITH CARON), making sure that the
entire string is encoded as [UTF-8]; the result is an XMPP "node
identifier" of "jiři".
3. Transform the string of US-ASCII characters that conforms to the
"host" rule into an XMPP "domain identifier" by converting the
US-ASCII string to [UTF-8] and converting the percent-encoded
representation "%C4%8C" to its equivalent [UTF-8] character
(LATIN SMALL LETTER C WITH CARON), making sure that the entire
string is encoded as [UTF-8]; the result is an XMPP "domain
identifier" of "čechy.example" (encoded as a [UTF-8]
string).
4. Transform the string of US-ASCII characters that conforms to the
"resid" rule into an XMPP "resource identifier" by converting the
percent-encoded representation "%20" to its equivalent [UTF-8]
character (SP), making sure that the entire string is encoded as
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[UTF-8]; the result is an XMPP "resource identifier" of "v
Praze".
5. Concatenate the following (ensuring that the resulting string is
encoded as [UTF-8]):
1. the XMPP "node identifier" and the "@" character
2. the XMPP "domain identifier"
3. the "/" character and the XMPP "resource identifier"
The result is this XMPP address:
<jiři@čechy.example/v Praze>
2.9 Internationalization
Because XMPP addresses are [UTF-8] strings and because the
non-US-ASCII octets in XMPP addresses can be easily converted to
percent-encoded octets, XMPP addresses are designed to work well with
Internationalized Resource Identifiers ([IRI]). In particular, with
the exception of stringprep verification and the conversion of
syntax-relevant US-ASCII characters (e.g., "?"), an XMPP IRI can be
constructed directly by prepending "xmpp:" to an XMPP address.
3. IANA Registration of xmpp: URI Scheme
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 "fragment", "host",
"pct-encoded", "query", "sub-delims", and "unreserved" rules are
defined in [URI].
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xmppuri = "xmpp:" hier-xmpp [ "?" querycomp ] [ "#" fragment ]
hier-xmpp = authpath / path-xmpp
authpath = "//" auth-xmpp [ "/" path-xmpp ]
auth-xmpp = nodeid "@" host
path-xmpp = [ nodeid "@" ] host [ "/" resid ]
nodeid = *( unreserved / pct-encoded / nodeallow )
nodeallow = "!" / "$" / "%" / "(" / ")" / "*" / "+" / ","
/ ";" / "=" / "^" / "`" / "{" / "|" / "}"
resid = *( unreserved / pct-encoded / sub-delims )
querycomp = querytype [ *pair ]
querytype = *( ALPHA / DIGIT / '-' / '_' / '.' / ':' )
pair = "&" key "=" value
key = *unreserved
value = *( unreserved / pct-encoded )
3.3 Character encoding considerations
Prior to any conversion into a URI and in accordance with
[XMPP-CORE], an Extensible Messaging and Presence Protocol (XMPP)
address MUST be represented as [UTF-8] by the generating application
(e.g., by transforming an application's internal representation of
the address as a UTF-16 string into a UTF-8 string). The UTF-8
string MUST then be converted into a US-ASCII string in order to be
included in a URI; as part of this conversion, non-US-ASCII octets
MUST be percent-encoded as described in Section 2.1 of [URI].
3.4 Intended usage
The xmpp: URI identifies entities that natively communicate using the
Extensible Messaging and Presence Protocol (XMPP), and is mainly used
for identification rather than processing. However, an application
that processes an xmpp: URI SHOULD reconstruct the encapsulated XMPP
address, authenticate with the appropriate XMPP server, and send an
appropriate XMPP "stanza" (XML fragment) to the XMPP address. There
is no MIME type associated with this URI.
3.5 Applications and/or protocols which use this URL scheme name
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 identify XMPP entities as full
URIs.
3.6 Security considerations
See Security Considerations (Section 5) of XXXX.
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3.7 Relevant publications
[XMPP-CORE]
3.8 Person and email address to contact for further information
Peter Saint-Andre [mailto:stpeter@jabber.org]
3.9 Author/change controller
This scheme is registered under the IETF tree. As such, the IETF
maintains change control.
4. IANA Considerations
This document registers a URI scheme. The registration template can
be found in Section 3 of this document.
5. Security Considerations
Detailed security considerations for Uniform Resource Identifiers are
given in [URI], and for the Extensible Messaging and Presence
Protocol 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 representation in
XMPP URIs. Care must also be taken in exposing XMPP addresses in the
authority and path components of XMPP URIs that are publicly
accessible.
6. References
6.1 Normative References
[ABNF] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[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 Identifier (URI): Generic Syntax",
draft-fielding-uri-rfc2396bis-07 (work in progress),
September 2004.
[URL-GUIDE]
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Internet-Draft XMPP-URI December 2004
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
Scheme Names", BCP 35, RFC 2717, November 1999.
[UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[XMPP-CORE]
Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
[XMPP-IM] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Instant Messaging and Presence", RFC
3921, October 2004.
6.2 Informative References
[CPIM] Peterson, J., "Common Profile for Instant Messaging
(CPIM)", RFC 3860, August 2004.
[CPP] Peterson, J., "Common Profile for Presence (CPP)", RFC
3859, August 2004.
[HTML] Raggett, D., "HTML 4.0 Specification", W3C REC
REC-html40-19980424, April 1998.
[HTTP-AUTH]
Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A. and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[IDNA] Faltstrom, P., Hoffman, P. and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 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.
[IRI] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", draft-duerst-iri-11 (work in
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Internet-Draft XMPP-URI December 2004
progress), December 2004.
[JEP-0009]
Adams, D., "Jabber-RPC", JSF JEP 0009, December 2002.
[JEP-0030]
Hildebrand, J., Millard, P., Eatmon, R. and P.
Saint-Andre, "Service Discovery", JSF JEP 0030, July 2004.
[JEP-0045]
Saint-Andre, P., "Multi-User Chat", JSF JEP 0045, October
2004.
[JEP-0053]
Saint-Andre, P., "Jabber Registrar", JSF JEP 0053, May
2004.
[JEP-0060]
Millard, P., "Publish-Subscribe", JSF JEP 0060, July 2004.
[JEP-0072]
Forno, F., "SOAP Over XMPP", JSF JEP 0072, May 2004.
[JEP-0077]
Saint-Andre, P., "In-Band Registration", JSF JEP 0077,
August 2004.
[JEP-0147]
Saint-Andre, P., "XMPP URI Query Components", JSF JEP
0147, November 2004.
[MAILTO] Hoffman, P., Masinter, L. and J. Zawinski, "The mailto URL
scheme", RFC 2368, July 1998.
[MIME] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996.
[NAMEPREP]
Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
Profile for Internationalized Domain Names (IDN)", RFC
3491, March 2003.
[STRINGPREP]
Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("STRINGPREP")", RFC 3454,
December 2002.
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[US-ASCII]
American National Standards Institute, "Coded Character
Set - 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986.
Author's Address
Peter Saint-Andre
Jabber Software Foundation
EMail: stpeter@jabber.org
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