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Versions: (draft-yoneya-precis-mappings) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 7790

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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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