Mapping characters for precis classes
draft-ietf-precis-mappings-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 7790.
|
|
|---|---|---|---|
| Authors | Yoshiro Yoneya , Takahiro Nemoto | ||
| Last updated | 2012-12-26 | ||
| Replaces | draft-yoneya-precis-mappings | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 7790 (Informational) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-precis-mappings-01
Network Working Group Y. YONEYA
Internet-Draft JPRS
Intended status: Informational T. NEMOTO
Expires: June 29, 2013 Keio University
December 26, 2012
Mapping characters for precis classes
draft-ietf-precis-mappings-01
Abstract
Preparation and comparison of internationalized strings ("precis")
framework [I-D.ietf-precis-framework] is defining several classes of
strings for preparation and comparison. In the document, case
mapping is defined because many of protocols handle case sensitive or
case insensitive string comparison and therefore preparation of
string is mandatory. As described in IDNA mapping [RFC5895] and
precis problem statement [I-D.ietf-precis-problem-statement],
mappings in internationalized strings are not limited to case, but
also width, delimiters and/or other specials are taken into
consideration. This document is a guideline for authors of protocol
profiles of precis framework and describes the mappings, that may be
performed before precis framework, that must be considered between
receiving user input and passing permitted code points to
internationalized protocols.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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."
This Internet-Draft will expire on June 29, 2013.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Types of mapping . . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol independent mapping . . . . . . . . . . . . . . . . . 5
3.1. Width mapping . . . . . . . . . . . . . . . . . . . . . . 5
4. Protocol dependent mapping . . . . . . . . . . . . . . . . . . 6
4.1. Delimiter mapping . . . . . . . . . . . . . . . . . . . . 6
4.2. Special mapping . . . . . . . . . . . . . . . . . . . . . 6
4.3. Local case mapping . . . . . . . . . . . . . . . . . . . . 6
5. Applying order of mapping . . . . . . . . . . . . . . . . . . 8
6. Open issues . . . . . . . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . 12
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Appendix A. Mapping type list each protocol . . . . . . . . . . . 15
A.1. Mapping type list for each protocol . . . . . . . . . . . 15
Appendix B. Codepoints which need special mapping . . . . . . . . 16
B.1. RFC3748 . . . . . . . . . . . . . . . . . . . . . . . . . 16
B.2. RFC4013 . . . . . . . . . . . . . . . . . . . . . . . . . 16
B.3. RFC4314 . . . . . . . . . . . . . . . . . . . . . . . . . 16
B.4. RFC4518 . . . . . . . . . . . . . . . . . . . . . . . . . 16
Appendix C. Code points list for local case mapping . . . . . . . 18
C.1. Unidode 6.2 . . . . . . . . . . . . . . . . . . . . . . . 18
Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 19
D.1. Changes since -00 . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
In many cases, user input of internationalized strings is generated
by input method editor ("IME") or copy-and-paste from free text.
Usually users do not care case and/or width of input characters
because they are identical for users' eyes. Further, users rarely
switch IME state to input special characters such as protocol
elements. For Internationalized Domain Names ("IDNs"), IDNA Mapping
[RFC5895] describes methods to treat these issues. For precis
strings, case mapping is defined as a process in precis framework
[I-D.ietf-precis-framework], but width mapping, delimiter mapping,
special mapping and language dependent mapping are not defined.
Handling of mappings other than case is also important to increase
chance of strings match as users expect. This document is a
guideline for authors of protocol profiles of precis framework and
describes the mappings that must be considered between receiving user
input and passing permitted code points to internationalized
protocols. Mappings that this document describes are expected to
perform before precis framework as well as Mapping Characters for
IDNA2008 [RFC5895].
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2. Types of mapping
This document defines two types of mapping. One is protocol
independent mapping that doesn't depend on protocol rules and the
other is protocol dependent mapping that depend on protocol rules.
This document defines some mappings in these mapping types. Authors
of protocol profiles of precis framework should need to give careful
consideration to choice of mappings.
Each mapping type is described in following sections.
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3. Protocol independent mapping
Protocol independent mapping is a mapping that doesn't depend on
protocol rules.
3.1. Width mapping
Fullwidth and halfwidth characters (those defined with Decomposition
Types <wide> and <narrow>) are mapped to their decomposition mappings
as shown in the Unicode character database [Unicode].
Width mapping will increase backward compatibility with Stringprep
[RFC3454] and precis framework [I-D.ietf-precis-framework]. Because
in a Stringprep profile which specifies Unicode normalization form KC
(NFKC) for normalization method, fullwidth/halfwidth characters are
mapped into its compatible form. If a precis framework profile
specified NFKC (which is not recommended), width mapping might not be
useful.
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4. Protocol dependent mapping
Protocol dependent mapping is a mapping that depend on protocol
rules.
4.1. Delimiter mapping
Definitions of delimiters in certain protocols are differ from each
other. Therefore, delimiter mapping table should be based on well
defined mapping table for each protocol.
One of the most useful case of delimiter mapping is when FULL STOP
character (U+002E) is a delimiter as well as domain name. Some of
IME generates FULL STOP compatible characters such as IDEOGRAPHIC
FULL STOP (U+3002) when users type FULL STOP on the keyboard.
4.2. Special mapping
Certain protocols have characters which need to map different
character from precis framework defined mapping rule other than
delimiter characters. In this document, these mappings are named
special mapping. They are differ from each protocol. Therefore,
special mapping table should be based on well defined mapping table
for each protocol. Examples of special mapping are following;
o White spaces are mapped to SPACE (U+0020)
o Some characters such as control characters are mapped to nothing
(Deletion)
LDAPprep[RFC4518] defines the rule that some codepoints(Appendix B.4)
are mapped to SPACE (U+0020).
4.3. Local case mapping
Local case mapping is case folding that depend on language context.
For example, given there is upper case I in a user ID strings, you
should care what's language context that this user ID depend on when
this character is mapped into lower case character. And if this
depends on Turkish, the character should be mapped into LATIN SMALL
LETTER DOTLESS I (U+0131) as this character's lower case.
This document defines characters that need local case mapping based
on the Specialcasing.txt [Specialcasing] in section 3.13 of The
Unicode Standerd [Unicode] to solve such a problem for precis
framework. Local case mapping targets only characters that get two
different results to perfom just casefolding that is defined in the
Casefolding.txt [Casefolding] and perfom special casefolding that is
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defined in the Specialcasing.txt then casefolding, because precis
framework have casefolding.
There are two types casefoldings defined as Unconditional Mappings
and Conditional Mappings in the Specialcasing.txt. Conditional
mappings have Language-Insensitive Mappings that targets characters
whose full case mappings do not depend on language, but do depend on
context and Language-Sensitive Mappings that these are characters
whose full case mappings depend on language and perhaps also context.
Of these mappings, characters that Unconditional Mappings and
Language-Insensitive Mappings in Conditional Mappings target are
mapped into same codepoint(s) with just casefolding and special
casefolding then casefolding. But characters that Language-Sensitive
Mappings in Conditional Mappings targets are mapped into different
codepoint with them. Therefore this document defined characters that
are a part of characters of Lithuanian(lt), Turkish(tr) and
Azerbaijanian(az) that Language-Sensitive Mappings targets as targets
for local case mapping.
Followings are the method to calculate codepoints that local case
mapping targets. Here Casefolding() means casefolding described in
the Casefolding.txt [Casefolding] and Specialcasing() means
specialcasing described in the Specialcasing.txt [Specialcasing].
If Casefolding(Specialcasing(cp)) != Casefolding(cp)
Then cp is a target
Else cp is not a target;
Appendix C "Code points list for local case mapping" lists codepoints
are calculated by this method.
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5. Applying order of mapping
Basically, applying order of mapping that this document describes
aren't sensitive. This section defines applying order of mapping to
minimize effect of codepoint change by mappings. This mapping order
is very general and was designed to be acceptable to the widest user
community.
1. Width mapping
2. Delimiter mapping
3. Special mapping
4. Local case mapping
Mappings that this document describes are expected to perform before
precis framework.
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6. Open issues
Followings are cullent open issues for this document.
1. Whether is local case mapping belong in additional mappings in
precis framework?
2. If local case mapping belong in precis framework, it's necessary
to specify mapping order as local case mapping then case mapping.
Because it makes no sense to perform local case mapping after
case mapping.
3. Handling order of precis framework and precis mappings is
ambiguous. It's necessary to define the order in precis
framework or in this document or in both documents.
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7. IANA Considerations
This document does not define any IANA-related things.
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8. Security Considerations
As well as Mapping Characters for IDNA2008 [RFC5895], this document
suggests creating mappings that might cause confusion for some users
while alleviating confusion in other users. Such confusion is not
covered in any depth in this document.
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9. Acknowledgment
Martin Duerst suggested a need for the case folding about the
mapping(map final sigma to sigma, German sz to ss,.).
Joe Hildebrand, John Klensin, Marc Blanchet, Pete Resnick and Peter
Saint-Andre, et al. gave important suggestion for this document
during at WG meeting.
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10. References
[RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
Internationalized Strings ("stringprep")", RFC 3454,
December 2002.
[RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names in Applications (IDNA)",
RFC 3490, March 2003.
[RFC3491] Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
Profile for Internationalized Domain Names (IDN)",
RFC 3491, March 2003.
[RFC3722] Bakke, M., "String Profile for Internet Small Computer
Systems Interface (iSCSI) Names", RFC 3722, April 2004.
[RFC3748] Aboba, B., Blunk, L., Vollbrecht, J., Carlson, J., and H.
Levkowetz, "Extensible Authentication Protocol (EAP)",
RFC 3748, June 2004.
[RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User Names
and Passwords", RFC 4013, February 2005.
[RFC4314] Melnikov, A., "IMAP4 Access Control List (ACL) Extension",
RFC 4314, December 2005.
[RFC4518] Zeilenga, K., "Lightweight Directory Access Protocol
(LDAP): Internationalized String Preparation", RFC 4518,
June 2006.
[RFC5895] Resnick, P. and P. Hoffman, "Mapping Characters for
Internationalized Domain Names in Applications (IDNA)
2008", RFC 5895, September 2010.
[RFC6122] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Address Format", RFC 6122, March 2011.
[I-D.ietf-precis-framework]
Saint-Andre, P. and M. Blanchet, "PRECIS Framework:
Preparation and Comparison of Internationalized Strings in
Application Protocols", draft-ietf-precis-framework-06
(work in progress), September 2012.
[I-D.ietf-precis-problem-statement]
Blanchet, M. and A. Sullivan, "Stringprep Revision and
PRECIS Problem Statement",
draft-ietf-precis-problem-statement-08 (work in progress),
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September 2012.
[Unicode] The Unicode Consortium, "The Unicode Standard, Version
6.2.0", <http://www.unicode.org/versions/Unicode6.2.0/>,
2012.
[Casefolding]
"CaseFolding-6.2.0.txt", Unicode Character Database, July
2011, <http://www.unicode.org/Public/6.2.0/ucd/
CaseFolding.txt>.
[Specialcasing]
"SpecialCasing-6.2.0.txt", Unicode Character Database,
July 2011, <http://www.unicode.org/Public/6.2.0/ucd/
SpecialCasing.txt>.
[ISO.3166-1]
International Organization for Standardization, "Codes for
the representation of names of countries and their
subdivisions - Part 1: Country codes", ISO Standard 3166-
1:1997, 1997.
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Appendix A. Mapping type list each protocol
A.1. Mapping type list for each protocol
This table is the mapping type list for each protocol. Values marked
"o" indicate that the protocol use the type of mapping. Values
marked "-" indicate that the protocol doesn't use the type of
mapping.
+----------------------+-------------+-----------+------+---------+
| \ Type of mapping | Width | Delimiter | Case | Special |
| RFC \ | (NFKC) | | | |
+----------------------+-------------+-----------+------+---------+
| 3490 | - | o | - | - |
| 3491 | o | - | o | - |
| 3722 | o | - | o | - |
| 3748 | o | - | - | o |
| 4013 | o | - | - | o |
| 4314 | o | - | - | o |
| 4518 | o | - | o | o |
| 6120 | - | - | o | - |
+----------------------+-------------+-----------+------+---------+
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Appendix B. Codepoints which need special mapping
B.1. RFC3748
Non-ASCII space characters [StringPrep, C.1.2] that can be mapped to
SPACE (U+0020).
B.2. RFC4013
Non-ASCII space characters [StringPrep, C.1.2] that can be mapped to
SPACE (U+0020).
B.3. RFC4314
Non-ASCII space characters [StringPrep, C.1.2] that can be mapped to
SPACE (U+0020).
B.4. RFC4518
Codepoints mapped to SPACE (U+0020) are following;
U+0009 (CHARACTER TABULATION)
U+000A (LINE FEED (LF))
U+000B (LINE TABULATION)
U+000C (FORM FEED (FF))
U+000D (CARRIAGE RETURN (CR))
U+0085 (NEXT LINE (NEL))
U+0020 (SPACE)
U+00A0 (NO-BREAK SPACE)
U+1680 (OGHAM SPACE MARK)
U+2000 (EN QUAD)
U+2001 (EM QUAD)
U+2002 (EN SPACE)
U+2003 (EM SPACE)
U+2004 (THREE-PER-EM SPACE)
U+2005 (FOUR-PER-EM SPACE)
U+2006 (SIX-PER-EM SPACE)
U+2007 (FIGURE SPACE)
U+2008 (PUNCTUATION SPACE)
U+2009 (THIN SPACE)
U+200A (HAIR SPACE)
U+2028 (Line Separator)
U+2029 (Paragraph Separator)
U+202F (NARROW NO-BREAK SPACE)
U+205F (MEDIUM MATHEMATICAL SPACE)
U+3000 (IDEOGRAPHIC SPACE)
All other control code (e.g., Cc) points or code points with a
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control function (e.g., Cf) are mapped to nothing. Codepoints mapped
to nothing that aren't specified by Stringprep are following;
U+0000-0008
U+000E-001F
U+007F-0084
U+0086-009F
U+06DD
U+070F
U+180E
U+200E-200F
U+202A-202E
U+2061-2063
U+206A-206F
U+FFF9-FFFB
U+1D173-1D17A
U+E0001
U+E0020-E007F
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Appendix C. Code points list for local case mapping
Followings are a list of characters that need Local case mapping.
Format:
<Language>; <Codepoint>; <Lowercase>; <Comments>
<Language> means the alpha-2 codes in [ISO.3166-1].
C.1. Unidode 6.2
lt; 0049; 0069 0307; LATIN CAPITAL LETTER I
lt; 004A; 006A 0307; LATIN CAPITAL LETTER J
lt; 012E; 012F 0307; LATIN CAPITAL LETTER I WITH OGONEK
lt; 00CC; 0069 0307 0300; LATIN CAPITAL LETTER I WITH GRAVE
lt; 00CD; 0069 0307 0301; LATIN CAPITAL LETTER I WITH ACUTE
lt; 0128; 0069 0307 0303; LATIN CAPITAL LETTER I WITH TILDE
tr; 0130; 0069; LATIN CAPITAL LETTER I WITH DOT ABOVE
tr; 0049; 0131; LATIN CAPITAL LETTER I
az; 0130; 0069; LATIN CAPITAL LETTER I WITH DOT ABOVE
az; 0049; 0131; LATIN CAPITAL LETTER I
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Appendix D. Change Log
D.1. Changes since -00
o Modify the Section 4.3 "Local case mapping" to specify the method
to calculate codepoints that local case mapping targets.
o Add the Section 6 "Open issues".
o Modify the Section 7 "IANA Considerations".
o Modify the Section 8 "Security Considerations".
o Remove the "The initial precis local case mapping registrations".
o Add the Appendix C "Code points list for local case mapping".
o Add the Appendix D "Change Log".
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Authors' Addresses
Yoshiro YONEYA
JPRS
Chiyoda First Bldg. East 13F
3-8-1 Nishi-Kanda
Chiyoda-ku, Tokyo 101-0065
Japan
Phone: +81 3 5215 8451
Email: yoshiro.yoneya@jprs.co.jp
Takahiro NEMOTO
Keio University
Graduate School of Media Design
4-1-1 Hiyoshi, Kohoku-ku
Yokohama, Kanagawa 223-8526
Japan
Phone: +81 45 564 2517
Email: t.nemo10@kmd.keio.ac.jp
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