RFC 2396, August 1998.
[RFC2397] Masinter, L., "The "data" URL scheme", RFC 2397,
August 1998.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee,
"Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616,
June 1999.
[RFC2640] Curtin, B., "Internationalization of the File Transfer
Protocol", RFC 2640, July 1999.
[RFC2718] Masinter, L., Alvestrand, H., Zigmond, D., and R.
Petke, "Guidelines for new URL Schemes", RFC 2718,
November 1999.
[UNIXML] Duerst, M. and A. Freytag, "Unicode in XML and other
Markup Languages", Unicode Technical Report #20, World
Wide Web Consortium Note, June 2003,
<http://www.w3.org/TR/unicode-xml/>.
[XLink] DeRose, S., Maler, E., and D. Orchard, "XML Linking
Language (XLink) Version 1.0", World Wide Web
Consortium Recommendation, June 2001,
<http://www.w3.org/TR/xlink/#link-locators>.
[XML1] Bray, T., Paoli, J., Sperberg-McQueen, C., Maler, E.,
and F. Yergeau, "Extensible Markup Language (XML) 1.0
(Third Edition)", World Wide Web Consortium
Recommendation, February 2004,
<http://www.w3.org/TR/REC-xml#sec-external-ent>.
[XMLNamespace] Bray, T., Hollander, D., and A. Layman, "Namespaces in
XML", World Wide Web Consortium Recommendation,
January 1999, <http://www.w3.org/TR/REC-xml-names>.
[XMLSchema] Biron, P. and A. Malhotra, "XML Schema Part 2:
Datatypes", World Wide Web Consortium Recommendation,
May 2001, <http://www.w3.org/TR/xmlschema-2/#anyURI>.
[XPointer] Grosso, P., Maler, E., Marsh, J. and N. Walsh,
"XPointer Framework", World Wide Web Consortium
Recommendation, March 2003,
<http://www.w3.org/TR/xptr-framework/#escaping>.
Appendix A. Design Alternatives
This section shortly summarizes major design alternatives and the
reasons for why they were not chosen.
Appendix A.1. New Scheme(s)
Introducing new schemes (for example, httpi:, ftpi:,...) or a new
metascheme (e.g., i:, leading to URI/IRI prefixes such as i:http:,
i:ftp:,...) was proposed to make IRI-to-URI conversion scheme
dependent or to distinguish between percent-encodings resulting from
IRI-to-URI conversion and percent-encodings from legacy character
encodings.
New schemes are not needed to distinguish URIs from true IRIs (i.e.,
IRIs that contain non-ASCII characters). The benefit of being able
to detect the origin of percent-encodings is marginal, as UTF-8 can
be detected with very high reliability. Deploying new schemes is
extremely hard, so not requiring new schemes for IRIs makes
deployment of IRIs vastly easier. Making conversion scheme dependent
is highly inadvisable and would be encouraged by separate schemes for
IRIs. Using a uniform convention for conversion from IRIs to URIs
makes IRI implementation orthogonal to the introduction of actual new
schemes.
Appendix A.2. Character Encodings Other Than UTF-8
At an early stage, UTF-7 was considered as an alternative to UTF-8
when IRIs are converted to URIs. UTF-7 would not have needed
percent-encoding and in most cases would have been shorter than
percent-encoded UTF-8.
Using UTF-8 avoids a double layering and overloading of the use of
the "+" character. UTF-8 is fully compatible with US-ASCII and has
therefore been recommended by the IETF, and is being used widely.
UTF-7 has never been used much and is now clearly being discouraged.
Requiring implementations to convert from UTF-8 to UTF-7 and back
would be an additional implementation burden.
Appendix A.3. New Encoding Convention
Instead of using the existing percent-encoding convention of URIs,
which is based on octets, the idea was to create a new encoding
convention; for example, to use "%u" to introduce UCS code points.
Using the existing octet-based percent-encoding mechanism does not
need an upgrade of the URI syntax and does not need corresponding
server upgrades.
Appendix A.4. Indicating Character Encodings in the URI/IRI
Some proposals suggested indicating the character encodings used in
an URI or IRI with some new syntactic convention in the URI itself,
similar to the "charset" parameter for e-mails and Web pages. As an
example, the label in square brackets in
"http://www.example.org/ros[iso-8859-1]é"; indicated that the
following "é"; had to be interpreted as iso-8859-1.
If UTF-8 is used exclusively, an upgrade to the URI syntax is not
needed. It avoids potentially multiple labels that have to be copied
correctly in all cases, even on the side of a bus or on a napkin,
leading to usability problems (and being prohibitively annoying).
Exclusively using UTF-8 also reduces transcoding errors and
confusion.
Authors’ Addresses
Martin Duerst (Note: Please write "Duerst" with u-umlaut wherever
possible, for example as "Dürst" in XML and
HTML.)
World Wide Web Consortium
5322 Endo
Fujisawa, Kanagawa 252-8520
Japan
Phone: +81 466 49 1170
Fax: +81 466 49 1171
EMail: duerst@w3.org
URI: http://www.w3.org/People/D%C3%BCrst/
(Note: This is the percent-encoded form of an IRI.)
Michel Suignard
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052
U.S.A.
Phone: +1 425 882-8080
EMail: michelsu@microsoft.com
URI: http://www.suignard.com
Full Copyright Statement
Copyright (C) The Internet Society (2005).
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
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the IETF’s procedures with respect to rights in IETF Documents can
be found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.