    Independent Submission                                    A. El-Sherbiny
    Request for Comments: 5564                                      M. Farah
    Category: Informational                                         UN-ESCWA
    ISSN: 2070-1721                                              I. Oueichek
                                                Syrian Telecom Establishment
                                                                 A. Al-Zoman
                                                              SaudiNIC, CITC
                                                               February 2010

                      Linguistic Guidelines for the Use of
                    the Arabic Language in Internet Domains

    Abstract

       This document constitutes technical specifications for the use of
       Arabic in Internet domain names and provides linguistic guidelines
       for Arabic domain names.  It addresses Arabic-specific linguistic
       issues pertaining to the use of Arabic language in domain names.

    Status of This Memo

       This document is not an Internet Standards Track specification; it is
       published for informational purposes.

       This is a contribution to the RFC Series, independently of any other
       RFC stream.  The RFC Editor has chosen to publish this document at
       its discretion and makes no statement about its value for
       implementation or deployment.  Documents approved for publication by
       the RFC Editor are not a candidate for any level of Internet
       Standard; see Section 2 of RFC 5741.

       Information about the current status of this document, any errata,
       and how to provide feedback on it may be obtained at
       http://www.rfc-editor.org/info/rfc5564.

    El-Sherbiny, et al.           Informational                     [Page 1]

    RFC 5564               Arabic Character Guidelines         February 2010

    Copyright Notice

       Copyright (c) 2010 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.

       This document may not be modified, and derivative works of it may not
       be created, except to format it for publication as an RFC or to
       translate it into languages other than English.

    Table of Contents

       1. Introduction ....................................................2
       2. Arabic Language-Specific Issues .................................3
          2.1. Linguistic Issues ..........................................4
               2.1.1. Diacritics (Tashkeel) and Shadda ....................4
               2.1.2. Kasheeda or Tatweel (Horizontal Character
                      Size Extension) .....................................5
               2.1.3. Character Folding ...................................5
          2.2. Supported Character Set ....................................6
          2.3. Arabic Linguistic Issues Affected by Technical
               Constraints ................................................8
               2.3.1. Numerals ............................................8
               2.3.2. The Space Character .................................8
       3. Summary and Conclusion ..........................................8
       4. Security Considerations .........................................9
       5. Acknowledgments .................................................9
       6. References ......................................................9
          6.1. Normative References .......................................9
          6.2. Informative References .....................................9

    1.  Introduction

       The Internet Engineering Task Force (IETF) issued in March 2003 a set
       of RFCs for Internationalized Domain Names (IDN) ([1], [2], and [3]),
       which were planned to become the de facto standard for all languages.
       In 2007 and 2008, the following working drafts were released that
       propose revisions to the IDNA protocol:

       o  Internationalized Domain Names for Applications (IDNA):
          Background, Explanation, and Rationale [5]

    El-Sherbiny, et al.           Informational                     [Page 2]

    RFC 5564               Arabic Character Guidelines         February 2010

       o  Internationalized Domain Names in Applications (IDNA): Protocol
          [6]

       o  An updated IDNA criterion for right-to-left scripts [7]

       o  The Unicode code points and IDNA [8]

       These documents are known collectively as "IDNA2008".

       This document constitutes a technical specification for the
       implementation of the IDN standards in the case of the Arabic
       language.  It will allow the use of standard language tables to write
       domain names in Arabic characters.  Therefore, it should be
       considered as a logical extension to the IDN standards.  It thus
       presents guidelines for the proper use of Arabic characters with the
       IDN standards in an Arabic language context.

       This document reflects the recommendations of the Arab Working Group
       on Arabic Domain Names (AWG-ADN), established by the League of Arab
       States (LAS), based on standardisation efforts of the United Nations
       Economic and Social Commission for Western Asia (UN-ESCWA) and on
       that group's document, "Guidelines for an Arabic Internet Domain
       Name" [9].  This document is also in full harmony with recent
       rigorous discussions that took place within the major language
       communities that use the Arabic script in their languages.

       This document provides guidelines for the ways Arabic characters may
       be used for registering Internet domain names and how linguistic-
       specific issues should be handled.  A few rules are recommended for
       application at the protocol level.

       The key words "MUST", "REQUIRED", "SHOULD", "RECOMMENDED", and "MAY"
       in this document are to be interpreted as described in RFC 2119 [4].

       Comments on this document are solicited and should be addressed to
       the working group's mailing list at ESCWA-ICTD@un.org and/or the
       author(s).

    2.  Arabic Language-Specific Issues

       The main objective of the creation of Arabic domain names is to have
       a vehicle to increase Internet use amongst all strata of the Arabic-
       speaking communities.

       Furthermore, a non-user-friendly domain name would further add to the
       ambiguity and the eccentricity of the Internet to the Arabic-speaking
       communities, thus contributing negatively to the spread of the

    El-Sherbiny, et al.           Informational                     [Page 3]

    RFC 5564               Arabic Character Guidelines         February 2010

       Internet and leading to further isolation of these communities at the
       global level.

       Hence, there have been intensive efforts (especially those
       spearheaded by Dr. Al-Zoman and contributed to by UN-ESCWA and its
       Arabic Domain Names Task Force (ADN-TF)) to reach consensus on a
       multitude of linguistic issues with the following goals:

       o  To define the accepted Arabic character set to be used for writing
          domain names in Arabic, which is the subject of this document.

       o  To define the top-level domains of the Arabic domain name tree
          structure (i.e., Arabic gTLDs and ccTLDs).  This goal will be
          handled in a separate document.

       The first meeting of the AWG-ADN, held in Damascus from January-
       February 2005, gave special attention to the following:

       o  Simplification of the domain names, whenever possible, to
          facilitate the interaction of the Arabic user with the Internet.

       o  Adoption of solutions that do not lead to confusion either in
          reading or in writing, provided that this does not compromise the
          linguistic correctness of used words.

       o  Mixing Arabic and non-Arabic letters in the domain name label is
          not acceptable.

    2.1.  Linguistic Issues

       There are a number of linguistic issues that have been proposed with
       respect to the use of the Arabic language in domain names.  This
       section will highlight some of them.  This section is based on the
       papers of Dr. Al-Zoman ([10] and [11]) and on the report of the first
       meeting of AWG-ADN [12].  For details, the reader is encouraged to
       review these references.

    2.1.1.  Diacritics (Tashkeel) and Shadda

       Tashkeel and Shadda are accent marks placed above or below Arabic
       letters to produce proper pronunciation.  They are thus used to
       differentiate different meanings for different words with the same
       base characters.

       Neither Tashkeel nor Shadda are permitted in zone files when
       registering domain names in the Arabic language, although they are
       permitted in the current edition of IDNA2008.  They can be supported

    El-Sherbiny, et al.           Informational                     [Page 4]

    RFC 5564               Arabic Character Guidelines         February 2010

       or ignored, if necessary, in the user interface with local mappings
       and can be stripped before IDNA processing.

       The following are their Unicode presentations:

          U+064B ARABIC FATHATAN
          U+064C ARABIC DAMMATAN
          U+064D ARABIC KASRATAN
          U+064E ARABIC FATHA
          U+064F ARABIC DAMMA
          U+0650 ARABIC KASRA
          U+0651 ARABIC SHADDA
          U+0652 ARABIC SUKUN

    2.1.2.  Kasheeda or Tatweel (Horizontal Character Size Extension)

       Kasheeda (U+0640 ARABIC TATWEEL) must not be used in Arabic domain
       names and should be disallowed for Arabic language domain names.  The
       Kasheeda is not a letter and does not have an effect on
       pronunciation.  It is used to extend the horizontal length or change
       the shape of the preceding letter for graphical representation
       purposes in Arabic writing.  Accordingly, it has no value for the
       writing of domain names.  The same applies to all languages using the
       Arabic script.  The authors recommend that it should be disallowed at
       the protocol level.

    2.1.3.  Character Folding

       Character folding is the process where multiple letters (that may
       have some similarity with respect to their shapes) are folded into
       one shape.  Examples of such Arabic characters include:

       o  Folding Teh Marbuta (U+0629) and Heh (U+0647) at the end of a word

       o  Folding different forms of Hamzah (U+0622, U+0623, U+0625, U+0627)

       o  Folding Alef Maksura (U+0649) and Yeh (U+064A) at the end of a
          word

       o  Folding Waw with Hamzah Above (U+0624) and Waw (U+0648)

       With respect to the Arabic language, character folding is not
       acceptable because it changes the meaning of words and is against the
       principle of spelling rules.  Replacing a character valid for use in
       domain names with another character also valid for use in domain
       names, which may have a similar shape, will give a different meaning.
       This will lead to only one word representing several words consisting

    El-Sherbiny, et al.           Informational                     [Page 5]

    RFC 5564               Arabic Character Guidelines         February 2010

       of all the combinations of folded characters.  Hence, the other words
       will be masked by a single word [10].

       Mis-spelling or handwriting errors do occur, leading to mixing
       different characters despite the fact that this is not the case in
       published and printed materials.  One of the motivations of this
       effort is to preserve the language, particularly with the spread of
       the globalization movement.  Within this context, character folding
       is working against this motivation since it is going to have a
       negative effect on the principle and ethics of the language.
       Technology should work to preserve the language and not to destroy
       it.  Thus, character folding should not be allowed.  The case of
       digits is treated in a separate section below.

    2.2.  Supported Character Set

       A domain name to be written in Arabic must be composed of a sequence
       of the following UNICODE characters and the FULL STOP (u+002E) to
       separate the labels.  These are based on UNICODE version 5.0.  The
       tables below are constructed using an inclusion-based approach.
       Thus, characters that are not part of these tables are prohibited.

                 +---------+-------------------------------------+
                 | Unicode | Character Name                      |
                 +---------+-------------------------------------+
                 | 0621    | ARABIC LETTER HAMZA                 |
                 | 0622    | ARABIC LETTER ALEF WITH MADDA ABOVE |
                 | 0623    | ARABIC LETTER ALEF WITH HAMZA ABOVE |
                 | 0624    | ARABIC LETTER WAW WITH HAMZA ABOVE  |
                 | 0625    | ARABIC LETTER ALEF WITH HAMZA BELOW |
                 | 0626    | ARABIC LETTER YEH WITH HAMZA ABOVE  |
                 | 0627    | ARABIC LETTER ALEF                  |
                 | 0628    | ARABIC LETTER BEH                   |
                 | 0629    | ARABIC LETTER TEH MARBUTA           |
                 | 062A    | ARABIC LETTER TEH                   |
                 | 062B    | ARABIC LETTER THEH                  |
                 | 062C    | ARABIC LETTER JEEM                  |
                 | 062D    | ARABIC LETTER HAH                   |
                 | 062E    | ARABIC LETTER KHAH                  |
                 | 062F    | ARABIC LETTER DAL                   |
                 | 0630    | ARABIC LETTER THAL                  |
                 | 0631    | ARABIC LETTER REH                   |
                 | 0632    | ARABIC LETTER ZAIN                  |
                 | 0633    | ARABIC LETTER SEEN                  |
                 | 0634    | ARABIC LETTER SHEEN                 |
                 | 0635    | ARABIC LETTER SAD                   |
                 | 0636    | ARABIC LETTER DAD                   |
                 | 0637    | ARABIC LETTER TAH                   |

    El-Sherbiny, et al.           Informational                     [Page 6]

    RFC 5564               Arabic Character Guidelines         February 2010

                 | 0638    | ARABIC LETTER ZAH                   |
                 | 0639    | ARABIC LETTER AIN                   |
                 | 063A    | ARABIC LETTER GHAIN                 |
                 | 0641    | ARABIC LETTER FEH                   |
                 | 0642    | ARABIC LETTER QAF                   |
                 | 0643    | ARABIC LETTER KAF                   |
                 | 0644    | ARABIC LETTER LAM                   |
                 | 0645    | ARABIC LETTER MEEM                  |
                 | 0646    | ARABIC LETTER NOON                  |
                 | 0647    | ARABIC LETTER HEH                   |
                 | 0648    | ARABIC LETTER WAW                   |
                 | 0649    | ARABIC LETTER ALEF MAKSURA          |
                 | 064A    | ARABIC LETTER YEH                   |
                 | 0660    | ARABIC-INDIC DIGIT ZERO             |
                 | 0661    | ARABIC-INDIC DIGIT ONE              |
                 | 0662    | ARABIC-INDIC DIGIT TWO              |
                 | 0663    | ARABIC-INDIC DIGIT THREE            |
                 | 0664    | ARABIC-INDIC DIGIT FOUR             |
                 | 0665    | ARABIC-INDIC DIGIT FIVE             |
                 | 0666    | ARABIC-INDIC DIGIT SIX              |
                 | 0667    | ARABIC-INDIC DIGIT SEVEN            |
                 | 0668    | ARABIC-INDIC DIGIT EIGHT            |
                 | 0669    | ARABIC-INDIC DIGIT NINE             |
                 +---------+-------------------------------------+

            Source: Supporting the Arabic Language in Domain Names [10]
             Table 1: CHARACTERS FROM UNICODE ARABIC TABLE (0600-06FF)

                           +---------+-----------------+
                           | Unicode | Digit Name      |
                           +---------+-----------------+
                           | 0030    | DIGIT ZERO      |
                           | 0031    | DIGIT ONE       |
                           | 0032    | DIGIT TWO       |
                           | 0033    | DIGIT THREE     |
                           | 0034    | DIGIT FOUR      |
                           | 0035    | DIGIT FIVE      |
                           | 0036    | DIGIT SIX       |
                           | 0037    | DIGIT SEVEN     |
                           | 0038    | DIGIT EIGHT     |
                           | 0039    | DIGIT NINE      |
                           | 002D    | HYPHEN-MINUS    |
                           +---------+-----------------+

            Source: Supporting the Arabic Language in Domain Names [10]
          Table 2: CHARACTERS FROM UNICODE BASIC LATIN TABLE (0000-007F)

    El-Sherbiny, et al.           Informational                     [Page 7]

    RFC 5564               Arabic Character Guidelines         February 2010

    2.3.  Arabic Linguistic Issues Affected by Technical Constraints

       In this section, technical aspects of some linguistic issues are
       discussed.

    2.3.1.  Numerals

       In the Arab countries, there are two sets of numerical digits used:

       o  Set I: (0, 1, 2, 3, 4, 5, 6, 7, 8, 9) mostly used in the western
          part of the Arab world.

       o  Set II: (u+0660, u+0661, u+0662, u+0663, u+0664, u+0665, u+0666,
          u+0667, u+0668, u+0669) mostly used in the eastern part of the
          Arab world.

       Both sets may be supported in the user interface; however, the rule
       of numeral homogeneity must be observed.  The rule specifies that
       digits from the Arabic-Indic set of numerals (u+0660 to u+0669)
       should not be allowed to mix with ASCII digits (u+0030 to u+0039)
       within the same Arabic domain name label.  Thus, the appearance of a
       digit from one set prevents the use of any other digit from the other
       set.

    2.3.2.  The Space Character

       The space character is strictly disallowed in domain names, as it is
       a control character.  Instead, the hyphen (Al-sharta, i.e., u+02D) is
       proposed as a separator between Arabic words to avoid confusion that
       can take place if the words are typed without a separator.

       It is acceptable to use the hyphen to separate between words within
       the same domain name label.

    3.  Summary and Conclusion

       The proposed guidelines are in full accordance with the IETF IDN
       standards and take into account Arabic-language-specific issues
       within a compromise between grammatical rules of the Arabic language
       and ease of use of that language on the Internet.

       In summary, the guidelines specify that, in Arabic domain names:

       o  Accent marks (Tashkeel and Shadda) are not permitted.

       o  Character folding is not permitted.

    El-Sherbiny, et al.           Informational                     [Page 8]

    RFC 5564               Arabic Character Guidelines         February 2010

       o  If a numeral from the Arabic-Indic or ASCII digit sets appears in
          a label, numeral homogeneity is required.

       o  The hyphen must be used as a word separator instead of space.

    4.  Security Considerations

       No particular security considerations could be identified regarding
       the use of Arabic characters in writing domain names.  In particular,
       any potential visual confusion between different character strings is
       avoided using the guidelines proposed in this document.

    5.  Acknowledgments

       ESCWA ICT Division provided support and funding for the development
       of this document with the objective of reaching a standard for
       comprehensive Arabic domain names.  Thanks are due to SaudiNIC for
       its continuous efforts in supporting the development of Arabic domain
       names.

       John Klensin and Harald Alvestrand reviewed the document and provided
       useful editorial and substantive support to enrich it.

    6.  References

    6.1.  Normative References

       [1]   Faltstrom, P., Hoffman, P., and A. Costello,
             "Internationalizing Domain Names in Applications (IDNA)", RFC
             3490, March 2003.

       [2]   Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep Profile
             for Internationalized Domain Names (IDN)", RFC 3491, March
             2003.

       [3]   Costello, A., "Punycode: A Bootstring encoding of Unicode for
             Internationalized Domain Names in Applications (IDNA)", RFC
             3492, March 2003.

       [4]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
             Levels", BCP 14, RFC 2119, March 1997.

    6.2.  Informative References

       [5]   Klensin, J., "Internationalized Domain Names for Applications
             (IDNA): Definitions, Background and Rationale", Work in
             Progress, September 2008.

    El-Sherbiny, et al.           Informational                     [Page 9]

    RFC 5564               Arabic Character Guidelines         February 2010

       [6]   Klensin, J., "Internationalized Domain Names in Applications
             (IDNA): Protocol", Work in Progress, September 2008.

       [7]   Alvestrand, H. and C. Karp, "An updated IDNA criterion for
             right-to-left scripts", Work in Progress, July 2008.

       [8]   Faltstrom, P., "The Unicode Codepoints and IDNA", Work in
             Progress, July 2008.

       [9]   United Nations Economic and Social Commission for Western Asia
             (UN-ESCWA), "Guidelines for an Arabic Domain Name System
             (ADNS)", Work in Progress, November 2007.

       [10]  Al-Zoman, A., "Supporting the Arabic Language in Domain Names",
             October 2003, <http://www.arabic-domains.org/docs/
             NIC-docs/SupportingArabicDomainNmaes.pdf>.

       [11]  Al-Zoman, A., "Arabic Top-Level Domains", Paper presented in
             Expert Group Meeting on Promotion of Digital Arabic Content,
             the United Nations, Economic and Social Commission for Western
             Asia, Beirut, June 2003.

       [12]  League of Arab States, "Report of the first meeting of AWG-ADN,
             Damascus", February 2005, <http://www.arabic-
             domains.org/ar/intrnational-entites.php>.

    El-Sherbiny, et al.           Informational                    [Page 10]

    RFC 5564               Arabic Character Guidelines         February 2010

    Authors' Addresses

       Ayman El-Sherbiny
       Information and Communication Technology Division ESCWA
       UN-House
       P.O. Box 11-8575
       Beirut
       Lebanon

       EMail: El-sherbiny@un.org

       Mansour Farah
       Information and Communication Technology Division ESCWA
       UN-House
       P.O. Box 11-8575
       Beirut
       Lebanon

       EMail: farah14@un.org

       Ibaa Oueichek
       Syrian Telecom Establishment
       Damascus
       Syria

       EMail: oueichek@scs-net.org

       Abdulaziz H. Al-Zoman, PhD
       SaudiNIC, General Directorate of Internet Services
       IT Sector, CITC
       King Abdulaziz City for Science and Technology
       PO Box 6086
       Riyadh  11442
       Saudi Arabia

       EMail: azoman@citc.gov.sa

    El-Sherbiny, et al.           Informational                    [Page 11]