[Docs] [txt|pdf|xml|html] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-yoneya-precis-mappings) 00 01 02 03 04 05 06 07 08

Network Working Group                                          Y. YONEYA
Internet-Draft                                                      JPRS
Intended status: Informational                                 T. Nemoto
Expires: February 08, 2014                               Keio University
                                                         August 07, 2013


                 Mapping characters for PRECIS classes
                     draft-ietf-precis-mappings-03

Abstract

   The framework for preparation and comparison of internationalized
   strings ("PRECIS") defines several classes of strings for preparation
   and comparison.  In the framework, case mapping is defined because
   many protocols handle case-sensitive or case-insensitive string
   comparison and therefore preparation of the string is mandatory.  As
   described in the mapping for Internationalized Domain Names in
   Applications (IDNA) and the PRECIS problem statement, mappings for
   internationalized strings are not limited to case, but also width
   mapping and mapping of delimiters and other specials can be taken
   into consideration.  This document provides guidelines for authors of
   protocol profiles of the PRECIS framework and describes several
   mappings that can be applied between receiving user input and passing
   permitted code points to internationalized protocols.  The mappings
   described here are expected to be applied as Additional mapping in the
   PRECIS framework.

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 February 08, 2014.

Copyright Notice





YONEYA & Nemoto         Expires February 08, 2014               [Page 1]

Internet-Draft               precis mapping                  August 2013


   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Protocol dependent mappings . . . . . . . . . . . . . . . . .   3
     2.1.  Delimiter mapping . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Special mapping . . . . . . . . . . . . . . . . . . . . .   3
     2.3.  Local case mapping  . . . . . . . . . . . . . . . . . . .   4
   3.  Order of operations . . . . . . . . . . . . . . . . . . . . .   5
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgment  . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Appendix A.  Mapping type list each protocol  . . . . . . . . . .   7
     A.1.  Mapping type list for each protocol . . . . . . . . . . .   7
   Appendix B.  Code points list for local case mapping  . . . . . .   7
     B.1.  Unicode 6.2 . . . . . . . . . . . . . . . . . . . . . . .   8
   Appendix C.  Change Log . . . . . . . . . . . . . . . . . . . . .   8
     C.1.  Changes since -00 . . . . . . . . . . . . . . . . . . . .   8
     C.2.  Changes since -01 . . . . . . . . . . . . . . . . . . . .   8
     C.3.  Changes since -02 . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   In many cases, user input of internationalized strings is generated
   through the use of an input method editor ("IME") or through copy-
   and-paste from free text.  Usually users do not care about the case
   and/or width of input characters because they appear to be visually
   identical.  Further, users rarely switch IME state to input special
   characters such as protocol elements.  For Internationalized Domain
   Names ("IDNs"), the IDNA Mapping specification [RFC5895] describes
   methods for handling these issues.  For PRECIS strings, case mapping
   and width mapping are defined in the PRECIS framework specification
   [I-D.ietf-precis-framework], but delimiter mapping, special mapping,
   and language dependent mapping are not defined.  Handling of mappings



YONEYA & Nemoto         Expires February 08, 2014               [Page 2]

Internet-Draft               precis mapping                  August 2013


   other than case and width is also important to increase chance of
   strings match as users expect.  This document provides guidelines for
   authors of protocol profiles of the PRECIS framework and describes
   mappings that can be applied between receiving user input and passing
   permitted code points to internationalized protocols.  The mappings
   described in this document are expected to be applied as Additional
   mapping in the PRECIS framework.

2.  Protocol dependent mappings

   The PRECIS framework defines several protocol-independent mappings.
   The additional mappings defined in this document are protocol-
   dependent, i.e., they depend on the rules for a particular
   application protocol.

2.1.  Delimiter mapping

   Some application protocols define delimiters for use in such
   protocols, but the delimiters are different for each protocols.
   Therefore, the delimiter mapping table should be based on a well-
   defined mapping table for each protocol.

   Delimiter mapping is supposed to map delimiter characters that have
   compatible characters to canonical characters.  For example, '@' in
   mail address or ':' and '/' in URI has width compatible character.
   And '+', '-', '<' and '>' may be such character.  Another example is
   the FULL STOP character (U+002E) which is a delimiter in the visual
   presentation of domain names.  Some IMEs generate semantic or width
   compatible character of FULL STOP such as IDEOGRAPHIC FULL STOP
   (U+3002) when a user types FULL STOP on the keyboard.  Such FULL STOP
   compatible characters need to be mapped to the FULL STOP before
   passing the string to the protocol.

2.2.  Special mapping

   Aside from delimiter characters, certain protocols have characters
   which need to be mapped in ways that are different from the rules
   specified in the PRECIS framework (e.g., mapping non-ASCII space
   characters to ASCII space).  In this document, these mappings are
   called "special mappings".  They are different for each protocol.
   Therefore, the special mapping table should be based on a well-
   defined mapping table for each protocol.  Examples of special mapping
   are the following;

   o  White spaces are mapped to SPACE (U+0020)

   o  Some characters such as control characters are mapped to nothing
      (Deletion)



YONEYA & Nemoto         Expires February 08, 2014               [Page 3]

Internet-Draft               precis mapping                  August 2013


   As examples, EAP [RFC3748], SASLprep [RFC4013], IMAP4 ACL [RFC4314]
   and LDAPprep [RFC4518] define the rule that some codepoints for non-
   ASCII space are mapped to SPACE (U+0020).

2.3.  Local case mapping

   Local case mapping is case folding that depends on language and
   context.  For example, the mapping of LATIN CAPITAL LETTER I (U+0049)
   depends on the language context of the user: if the language is
   Turkish (or one of several other languages), the character should be
   mapped into LATIN SMALL LETTER DOTLESS I (U+0131) as this character's
   lower case equivalent.

   To solve such problems for PRECIS framework, this document defines
   characters that need local case mapping based on the
   Specialcasing.txt [Specialcasing] file in section 3.13 of The Unicode
   Standard [Unicode].  Local case mapping targets only characters that
   get two different results to perform just casefolding that is defined
   in the Casefolding.txt [Casefolding] and perform special casefolding
   that is 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 file.  Conditional
   mappings have Language-Insensitive Mappings that target characters
   whose full case mappings do not depend on language, but do depend on
   context.  Language-Sensitive Mappings that these are characters whose
   full case mappings depend on language and perhaps also context.

   Of these mappings, characters with Unconditional Mappings or with
   Language-Insensitive Mappings in Conditional Mappings target are
   mapped into same codepoint(s) with just casefolding or special
   casefolding then casefolding.  But characters with Language-Sensitive
   Mappings in Conditional Mappings targets are mapped into different
   codepoints.  Therefore this document defines 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.

   The following are the methods to calculate codepoints that local case
   mapping targets.  Here Casefolding() means casefolding described in
   the Casefolding.txt file [Casefolding] and Specialcasing() means
   specialcasing described in the Specialcasing.txt file
   [Specialcasing].

   If Casefolding(Specialcasing(cp)) != Casefolding(cp)
   Then cp is a target
   Else cp is not a target;



YONEYA & Nemoto         Expires February 08, 2014               [Page 4]

Internet-Draft               precis mapping                  August 2013


   Application developers should calculate codepoints that local case
   mapping targets by using the latest Casefolding.txt and
   Specialcasing.txt.  Appendix B "Code points list for local case
   mapping" lists codepoints in Unicode 6.2 calculated by this method.

3.  Order of operations

   The mappings described in this document are expected to be applied as
   Additional mapping in the PRECIS framework.  Basically, the mappings
   described in this document describes could be applied in any order.
   However, this section specifies a particular order to minimize the
   effect of codepoint changes introduced by the mappings.  This mapping
   order is very general and was designed to be acceptable to the widest
   user community.

   1.  Delimiter mapping

   2.  Special mapping

   3.  Local case mapping

4.  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.

5.  IANA Considerations

   This document has no actions for the IANA.

6.  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.

7.  References

   [RFC3454]  Hoffman, P. and M. Blanchet, "Preparation of
              Internationalized Strings ("stringprep")", RFC 3454,
              December 2002.





YONEYA & Nemoto         Expires February 08, 2014               [Page 5]

Internet-Draft               precis mapping                  August 2013


   [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.

   [RFC6885]  Blanchet, M. and A. Sullivan, "Stringprep Revision and
              Problem Statement for the Preparation and Comparison of
              Internationalized Strings (PRECIS)", RFC 6885, March 2013.

   [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.

   [Unicode]  The Unicode Consortium, ., "The Unicode Standard, Version
              6.2.0", <http://www.unicode.org/versions/Unicode6.2.0/>,
              2012.

   [Casefolding]




YONEYA & Nemoto         Expires February 08, 2014               [Page 6]

Internet-Draft               precis mapping                  August 2013


              , "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.

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  |    -    |
   +----------------------+-------------+-----------+------+---------+


Appendix B.  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].





YONEYA & Nemoto         Expires February 08, 2014               [Page 7]

Internet-Draft               precis mapping                  August 2013


B.1.  Unicode 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

Appendix C.  Change Log

C.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".

C.2.  Changes since -01

   o  Unified PRECIS notation in all capital letters as well as other
      documents.

   o  Removed the Section 1 "Types of mapping" and the Section 2
      "Protocol independent mapping" because width mapping is now in
      framework document.

   o  Added relationship between the framework document and this
      document in the Section 3 "Order of operations".

   o  Updated the Section 4 "Open issues" to address new issue raised on
      mailing list.





YONEYA & Nemoto         Expires February 08, 2014               [Page 8]

Internet-Draft               precis mapping                  August 2013


   o  Move the Section 6 "IANA Considerations" after the Section 5
      "Security Considerations".

   o  Remove the Appendix B "Codepoints which need special mapping" and
      mentioned related documents in the Section 2.2 .

C.3.  Changes since -02

   o  Removed the "Open issues".

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



















YONEYA & Nemoto         Expires February 08, 2014               [Page 9]


Html markup produced by rfcmarkup 1.108, available from http://tools.ietf.org/tools/rfcmarkup/