📄 rfc4482.txt
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<xs:element name="homepage" type="xs:anyURI"/>
<xs:element name="icon" type="xs:anyURI"/>
<xs:element name="map" type="xs:anyURI"/>
<xs:element name="sound" type="xs:anyURI"/>
</xs:schema>
Figure 1: CIPID schema
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RFC 4482 CIPID July 2006
6. IANA Considerations
This document calls for IANA to register a new XML namespace URN and
schema per [6].
6.1. URN Sub-Namespace Registration for
'urn:ietf:params:xml:ns:pidf:cipid'
URI: urn:ietf:params:xml:ns:pidf:cipid
Description: This is the XML namespace for XML elements defined by
RFC 4482 to describe contact information presence information
extensions for the status element in the PIDF presence document
format in the application/pidf+xml content type.
Registrant Contact: IETF, SIMPLE working group, simple@ietf.org;
Henning Schulzrinne, hgs@cs.columbia.edu
XML:
BEGIN
<?xml version="1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML Basic 1.0//EN"
"http://www.w3.org/TR/xhtml-basic/xhtml-basic10.dtd">
<html xmlns="http://www.w3.org/1999/xhtml
<head>
<meta http-equiv="content-type"
content="text/html;charset=iso-8859-1"/>
<title>CIPID: Contact Information for the Presence Information
Data Format</title>
</head>
<body>
<h1>Namespace for contact information presence extension
(status)</h1>
<h2>urn:ietf:params:xml:ns:pidf:cipid</h2>
<p>See <a href="http://www.rfc-editor.org/rfc/rfc4482.txt">
RFC4482</a>.</p>
</body>
</html>
END
6.2. Schema Registration for Schema 'urn:ietf:params:xml:ns:pidf:cipid'
URI: urn:ietf:params:xml:ns:pidf:cipid
Registrant Contact: IESG
XML: See Figure 1
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RFC 4482 CIPID July 2006
7. Internationalization Considerations
CIPID delivers only URLs, except for the <display-name> element. The
resolution of the URLs can negotiate appropriate language and
character sets within the URL-designated protocol.
For the display name and to handle Internationalized Resource
Identifiers (IRIs) [16], since CIPID is represented in XML, it
provides native support for encoding information using the Unicode
character set and its more compact representations including UTF-8.
Conformant XML processors recognize both UTF-8 and UTF-16. Though
XML includes provisions to identify and use other character encodings
through use of an "encoding" attribute in an <?xml?> declaration, use
of UTF-8 is RECOMMENDED in environments where parser encoding support
incompatibility exists.
The XML 'xml:lang' attribute can be used to identify the language and
script for the <display-name> element. The specification allows
multiple occurrences of this element so that the presentity can
convey display names in multiple scripts and languages. If no 'xml:
lang' attribute is provided, the default value is "i-default" [3].
8. Security Considerations
The security issues are similar to those for RPID [11]. Watchers
need to restrict which content types of content pointed to by <icon>,
<homepage>, <map>, <sound>, and <vcard> elements they render.
Also, when a watcher accesses these URIs, the presentity may deduce
that the watcher is currently using the presence application. Thus,
a presence application concerned about leaking this information may
want to cache these objects for later use. (A presentity could
easily customize the URLs for each watcher, so that it can tell who
is referencing the objects.) This caching behavior may cause the
information to become stale, out-of-sync with the current data until
the cache is refreshed. Fortunately, the elements in CIPID are
expected to retain the same content for periods measured in days, so
that privacy-conscious applications may well decide to perform
caching over durations that reveal little current activity
information. Presentities need to keep in mind that clients may
cache the content referenced by URIs for long periods as they use
their presence system to construct presence documents using this
extension. If the referenced content needs to change frequently, the
presentity could, for example, update the presence document with a
new URI to encourage clients to notice.
Schulzrinne Standards Track [Page 8]
RFC 4482 CIPID July 2006
Icons and other URIs in this document could be used as a covert
channel to convey messages to the watcher, outside the content
monitoring that might be in place for instant messages or other
communications channels. Thus, entities that worry about such
channels may want to prohibit the usage of URLs pointing to resources
outside their domain, for example.
Implementors must take care to adhere to the mechanisms for verifying
the identity in the referenced server's certificate against the URI.
For instance, if the URI scheme is https, the requirements of RFC
2818 [5], section 3.1, must be met. In particular, the domain
represented in the URI must match the subjectAltName in the
certificate presented by the referenced server. If this identity
check fails, the referenced content SHOULD NOT be retrieved and MUST
NOT be used.
9. References
9.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Moats, R., "URN Syntax", RFC 2141, May 1997.
[3] Alvestrand, H., "IETF Policy on Character Sets and Languages",
BCP 18, RFC 2277, January 1998.
[4] Moats, R., "A URN Namespace for IETF Documents", RFC 2648,
August 1999.
[5] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[6] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January
2004.
[7] Maloney, M., Beech, D., Thompson, H., and N. Mendelsohn, "XML
Schema Part 1: Structures Second Edition", W3C REC REC-
xmlschema-1-20041028, October 2004.
[8] Malhotra, A. and P. Biron, "XML Schema Part 2: Datatypes Second
Edition", W3C REC REC-xmlschema-2-20041028, October 2004.
[9] Sugano, H., Fujimoto, S., Klyne, G., Bateman, A., Carr, W., and
J. Peterson, "Presence Information Data Format (PIDF)", RFC
3863, August 2004.
Schulzrinne Standards Track [Page 9]
RFC 4482 CIPID July 2006
[10] Yergeau, F., Paoli, J., Sperberg-McQueen, C., Bray, T., and E.
Maler, "Extensible Markup Language (XML) 1.0 (Third Edition)",
W3C REC REC-xml-20040204, February 2004.
9.2. Informative References
[11] Schulzrinne, H., Gurbani, V., Kyzivat, P., and J. Rosenberg,
"RPID: Rich Presence Extensions to the Presence Information Data
Format (PIDF)", RFC 4480, July 2006.
[12] Schulzrinne, H., "Timed Presence Extensions to the Presence
Information Data Format (PIDF) to Indicate Status Information
for Past and Future Time Intervals", RFC 4481, July 2006.
[13] Rosenberg, J., "A Data Model for Presence", RFC 4479, July 2006.
[14] Dawson, F. and T. Howes, "vCard MIME Directory Profile", RFC
2426, September 1998.
[15] Good, G., "The LDAP Data Interchange Format (LDIF) - Technical
Specification", RFC 2849, June 2000.
[16] Duerst, M. and M. Suignard, "Internationalized Resource
Identifiers (IRIs)", RFC 3987, January 2005.
Acknowledgements
This document is based on discussions within the IETF SIMPLE working
group. Spencer Dawkins, Vijay Gurbani, Avshalom Houri, Hisham
Khartabil, Paul Kyzivat, Eva Leppanen, Mikko Lonnfors, Aki Niemi, Jon
Peterson, Jonathan Rosenberg, and Robert Sparks provided helpful
comments.
Author's Address
Henning Schulzrinne
Columbia University
Department of Computer Science
450 Computer Science Building
New York, NY 10027
US
Phone: +1 212 939 7004
EMail: hgs+simple@cs.columbia.edu
URI: http://www.cs.columbia.edu
Schulzrinne Standards Track [Page 10]
RFC 4482 CIPID July 2006
Full Copyright Statement
Copyright (C) The Internet Society (2006).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
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OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
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INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
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Acknowledgement
Funding for the RFC Editor function is provided by the IETF
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Schulzrinne Standards Track [Page 11]
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