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Versions: 00 01 02 03 draft-ietf-precis-mappings

Network Working Group                                          Y. YONEYA
Internet-Draft                                                      JPRS
Intended status: Informational                          October 24, 2011
Expires: April 26, 2012

                 Mapping characters for PRECIS classes


   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 and/or delimiters are taken into consideration.  This
   document considers mappings other than case mapping in PRECIS

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on April 26, 2012.

Copyright Notice

   Copyright (c) 2011 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

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   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
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   described in the Simplified BSD License.

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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 and/or delimiter
   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.

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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

2.2.  Delimiter mapping

   Definitions of delimiters in certain protocols are differ from each
   other.  Therefore, delimiter mapping 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.

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3.  Discussion

   There are several points for discussion on this topic.

   o  Whether mappings other than case are targets of PRECIS or not?

   o  If they are target, are they a part of PRECIS Framework
      [I-D.ietf-precis-framework] or separate ones like IDNA Mapping

   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?

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4.  IANA Considerations


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5.  Security Considerations


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6.  References

   [RFC5895]  Resnick, P. and P. Hoffman, "Mapping Characters for
              Internationalized Domain Names in Applications (IDNA)
              2008", RFC 5895, September 2010.

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

              Blanchet, M. and P. Saint-Andre, "PRECIS Framework:
              Handling Internationalized Strings in Protocols",
              draft-ietf-precis-framework-00 (work in progress),
              August 2011.

              Blanchet, M. and A. Sullivan, "Stringprep Revision Problem
              Statement", draft-ietf-precis-problem-statement-03 (work
              in progress), July 2011.

   [Unicode]  The Unicode Consortium, "The Unicode Standard, Version
              6.0.0",  http://www.unicode.org/versions/Unicode6.0.0/,

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Author's Address

   Yoshiro YONEYA
   Chiyoda First Bldg. East 13F
   3-8-1 Nishi-Kanda
   Chiyoda-ku, Tokyo  101-0065

   Phone: +81 3 5215 8451
   Email: yoshiro.yoneya@jprs.co.jp

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