Network Working Group Y. YONEYA Internet-Draft JPRS Intended status: Informational T. Nemoto Expires: April 21, 2014 Keio University October 18, 2013 Mapping characters for PRECIS classes draft-ietf-precis-mappings-04 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 April 21, 2014. Copyright Notice YONEYA & Nemoto Expires April 21, 2014 [Page 1] Internet-Draft precis mapping October 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 . . . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 7.2. Informative References . . . . . . . . . . . . . . . . . 6 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 6.3 . . . . . . . . . . . . . . . . . . . . . . . 7 Appendix C. Change Log . . . . . . . . . . . . . . . . . . . . . 8 C.1. Changes since -00 . . . . . . . . . . . . . . . . . . . . 8 C.2. Changes since -01 . . . . . . . . . . . . . . . . . . . . 8 C.3. Changes since -02 . . . . . . . . . . . . . . . . . . . . 9 C.4. Changes since -03 . . . . . . . . . . . . . . . . . . . . 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. Users in general do not care about the case and/or width of input characters because they consider those characters to be functionally equivalent or visually identical. Furthermore, users rarely switch IME state to input special characters such as protocol elements. For Internationalized Domain Names ("IDNs"), the IDNA Mapping specification [RFC5895] describes YONEYA & Nemoto Expires April 21, 2014 [Page 2] Internet-Draft precis mapping October 2013 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 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; YONEYA & Nemoto Expires April 21, 2014 [Page 3] Internet-Draft precis mapping October 2013 o White spaces are mapped to SPACE (U+0020) o Some characters such as control characters are mapped to nothing (Deletion) 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 The purpose of local case mapping is to increase the probability of matching-result from the comparison between uppercase and lowercase characters, targeting locale and locale and context-dependent characters. As an example of locale and context-dependent mapping, LATIN CAPITAL LETTER I (U+0049) is normally mapped to LATIN SMALL LETTER I ((U+0069); however, if the language is Turkish (or one of several other languages), unless an I is before a dot_above, then the character should be mapped to LATIN SMALL LETTER DOTLESS I (U+0131). 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]. The following are the methods to calculate codepoints that local case mapping targets. Here Casefolding() means full 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; Local case mapping can be selected only when case mapping is selected using the PRECIS Framework profile. 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 6.3 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 YONEYA & Nemoto Expires April 21, 2014 [Page 4] Internet-Draft precis mapping October 2013 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,.). Alexey Melnikov, Andrew Sullivan, Joe Hildebrand, John Klensin, Marc Blanchet, Pete Resnick and Peter Saint-Andre, et al. gave important suggestion for this document during at WG meeting and WG LC. 7. References 7.1. Normative References [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 6.3.0", , 2012. [Casefolding] YONEYA & Nemoto Expires April 21, 2014 [Page 5] Internet-Draft precis mapping October 2013 , "CaseFolding-6.3.0.txt", Unicode Character Database, July 2011, , . [Specialcasing] , "SpecialCasing-6.3.0.txt", Unicode Character Database, July 2011, , . 7.2. Informative 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. YONEYA & Nemoto Expires April 21, 2014 [Page 6] Internet-Draft precis mapping October 2013 [RFC6885] Blanchet, M. and A. Sullivan, "Stringprep Revision and Problem Statement for the Preparation and Comparison of Internationalized Strings (PRECIS)", RFC 6885, March 2013. [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: ; ; ; means the alpha-2 codes in [ISO.3166-1]. B.1. Unicode 6.3 0049; 0069 0307; lt More_Above; # LATIN CAPITAL LETTER I 004A; 006A 0307; lt More_Above; # LATIN CAPITAL LETTER J 00CC; 0069 0307 0300; lt; # LATIN CAPITAL LETTER I WITH GRAVE 00CD; 0069 0307 0301; lt; # LATIN CAPITAL LETTER I WITH ACUTE 0128; 0069 0307 0303; lt; # LATIN CAPITAL LETTER I WITH TILDE YONEYA & Nemoto Expires April 21, 2014 [Page 7] Internet-Draft precis mapping October 2013 012E; 012F 0307; lt More_Above; # LATIN CAPITAL LETTER I WITH OGONEK 0307; 0307; lt After_Soft_Dotted; # COMBINING DOT ABOVE 0049; 0131; tr Not_Before_Dot; # LATIN CAPITAL LETTER I 0130; 0069; tr; # LATIN CAPITAL LETTER I WITH DOT ABOVE 0307; ; tr After_I; # COMBINING DOT ABOVE 0049; 0131; az Not_Before_Dot; # LATIN CAPITAL LETTER I 0130; 0069; az; # LATIN CAPITAL LETTER I WITH DOT ABOVE 0307; ; az After_I; # COMBINING DOT ABOVE 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. o Move the Section 6 "IANA Considerations" after the Section 5 "Security Considerations". YONEYA & Nemoto Expires April 21, 2014 [Page 8] Internet-Draft precis mapping October 2013 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". C.4. Changes since -03 o Modify the Section 1 "Introduction" in more clear text. o Modify the Section 2.3 "Local case mapping" to clarify the purpose of the local case mapping and an example, and add restriction to use with PRECIS Framework. o Change the format in the Appendix B "Code points list for local case mapping". o Split the Section 7 "References" into "Normative References" and "Informative References" o Update the Unicode version 6.2 to 6.3 in this document. 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 April 21, 2014 [Page 9]