Mapping characters for PRECIS classes
draft-yoneya-precis-mappings-01

Network Working Group                                          Y. YONEYA
Internet-Draft                                                      JPRS
Intended status: Informational                                 T. NEMOTO
Expires: August 13, 2012                                 Keio University
                                                       February 10, 2012

                 Mapping characters for PRECIS classes
                    draft-yoneya-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 considers mappings other than case
   mapping in PRECIS context.

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 August 13, 2012.

Copyright Notice

   Copyright (c) 2012 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

YONEYA & NEMOTO          Expires August 13, 2012                [Page 1]
Internet-Draft               PRECIS mapping                February 2012

   (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.

YONEYA & NEMOTO          Expires August 13, 2012                [Page 2]
Internet-Draft               PRECIS mapping                February 2012

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
   and/or special mapping are not defined.  Handling of mappings other
   than case is also important to increase chance of strings match as
   users expect.  This document considers such mappings in PRECIS
   context.

YONEYA & NEMOTO          Expires August 13, 2012                [Page 3]
Internet-Draft               PRECIS mapping                February 2012

2.  Type of mappings

2.1.  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].  This mapping
   should be performed before case mapping because fullwidth/halfwidth
   characters includes both upper case and lower case letters.

   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.

2.2.  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 protocols.  This mapping should be
   performed after width mapping because some punctuations have
   fullwidth form.

   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.

2.3.  Special mapping

   Certain protocols defined special mapping.  And they are differ from
   each other.  Therefore, special mapping table should be based on well
   defined mapping table for each protocols.  For example,
   LDAPprep[RFC4518] defines the rule that some codepoints(Appendix B.4)
   are mapped to SPACE (U+0020).  This mapping should be performed after
   width mapping because some punctuations have fullwidth form.  But,
   there is no preferred order of delimiter mapping and special mapping.
   See Section 3 for more detail.

YONEYA & NEMOTO          Expires August 13, 2012                [Page 4]
Internet-Draft               PRECIS mapping                February 2012

3.  Discussion

   There are several points for discussion on this topic.

   o  Is delimiter mapping a part of special mapping?  If it is not a
      part of special mapping, whether order of handling about special
      mapping should be performed before or after delimiter mapping?
      Are delimiters and other specials mutually orthogonal?  If they
      are, their order of handling is not important.  But if not, how is
      their order of handling made?

   o  Is additional case mapping considered?  Does the case folding for
      special characters (final sigma(U+03C2), German sz(U+00DF),
      Turkish I with dot above(U+0130), or dotless i(U+0131) ...) need
      special handling?

   o  Whether mappings other than case are targets of PRECIS or not?  If
      they are target, are they a part of PRECIS Framework
      [I-D.ietf-precis-framework] or separate ones like IDNA Mapping
      [RFC5895] specification?

   o  Are there another mappings not described in this document?  For
      example, migration from Stringprep [RFC3454] to PRECIS Framework
      [I-D.ietf-precis-framework] needs some special treatment?

YONEYA & NEMOTO          Expires August 13, 2012                [Page 5]
Internet-Draft               PRECIS mapping                February 2012

4.  IANA Considerations

   TBD.

YONEYA & NEMOTO          Expires August 13, 2012                [Page 6]
Internet-Draft               PRECIS mapping                February 2012

5.  Security Considerations

   TBD.

YONEYA & NEMOTO          Expires August 13, 2012                [Page 7]
Internet-Draft               PRECIS mapping                February 2012

6.  Acknowledgment

   Martin Duerst suggested a need for the case folding about the
   mapping(map final sigma to sigma, German sz to ss,.).

YONEYA & NEMOTO          Expires August 13, 2012                [Page 8]
Internet-Draft               PRECIS mapping                February 2012

7.  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]
              Blanchet, M. and P. Saint-Andre, "PRECIS Framework:
              Handling Internationalized Strings in Protocols",
              draft-ietf-precis-framework-01 (work in progress),
              October 2011.

   [I-D.ietf-precis-problem-statement]
              Blanchet, M. and A. Sullivan, "Stringprep Revision Problem
              Statement", draft-ietf-precis-problem-statement-04 (work
              in progress), January 2012.

YONEYA & NEMOTO          Expires August 13, 2012                [Page 9]
Internet-Draft               PRECIS mapping                February 2012

   [Unicode]  The Unicode Consortium, "The Unicode Standard, Version
              6.1.0",  http://www.unicode.org/versions/Unicode6.1.0/,
              2012.

YONEYA & NEMOTO          Expires August 13, 2012               [Page 10]
Internet-Draft               PRECIS mapping                February 2012

Appendix A.  Mapping type list each protocols

A.1.  Mapping type list for each protocols

   This table is the mapping type list for each protocols.  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  |    -    |
   +----------------------+-------------+-----------+------+---------+

YONEYA & NEMOTO          Expires August 13, 2012               [Page 11]
Internet-Draft               PRECIS mapping                February 2012

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

YONEYA & NEMOTO          Expires August 13, 2012               [Page 12]
Internet-Draft               PRECIS mapping                February 2012

   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

YONEYA & NEMOTO          Expires August 13, 2012               [Page 13]
Internet-Draft               PRECIS mapping                February 2012

Appendix C.  Change Log

C.1.  Changes since -00

   o  Add the Section 2.3 "Special mapping" in Section 2 Type of
      mappings.

   o  Add the topic about the special mapping and additional case
      mapping in Section 3 Discussion.

   o  Add Appendices;
      Appendix A "Mapping type list each protocols"
      Appendix B "Code point list is need special mapping"
      Appendix C "Change Log"

   o  Add the Section 6 Acknowledgment.

YONEYA & NEMOTO          Expires August 13, 2012               [Page 14]
Internet-Draft               PRECIS mapping                February 2012

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
   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 August 13, 2012               [Page 15]