GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc3743

Network Working Group K. Konishi Request for Comments: 3743 K. Huang Category: Informational H. Qian

                                                                 Y. Ko
                                                            April 2004
            Joint Engineering Team (JET) Guidelines for
       Internationalized Domain Names (IDN) Registration and
          Administration for Chinese, Japanese, and Korean

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2004).  All Rights Reserved.

IESG Note

 The IESG congratulates the Joint Engineering Team (JET) on developing
 mechanisms to enforce their desired policy.  The Language Variant
 Table mechanisms described here allow JET to enforce language-based
 character variant preferences, and they set an example for those who
 might want to use variant tables for their own policy enforcement.
 The IESG encourages those following this example to take JET's
 diligence as an example, as well as its technical work.  To follow
 their example, registration authorities may need to articulate
 policy, develop appropriate procedures and mechanisms for
 enforcement, and document the relationship between the two.  JET's
 LVT mechanism should be adaptable to different policies, and can be
 considered during that development process.
 The IETF does not, of course, dictate policy or require the use of
 any particular mechanisms for the implementation of these policies,
 as these are matters of sovereignty and contract.

Abstract

 Achieving internationalized access to domain names raises many
 complex issues.  These are associated not only with basic protocol
 design, such as how names are represented on the network, compared,
 and converted to appropriate forms, but also with issues and options
 for deployment, transition, registration, and administration.

Konishi, et al. Informational [Page 1] RFC 3743 JET Guidelines for IDN April 2004

 The IETF Standards for Internationalized Domain Names, known as
 "IDNA", focuses on access to domain names in a range of scripts that
 is broader in scope than the original ASCII.  The development process
 made it clear that use of characters with similar appearances and/or
 interpretations created potential for confusion, as well as
 difficulties in deployment and transition.  The conclusion was that,
 while those issues were important, they could best be addressed
 administratively rather than through restrictions embedded in the
 protocols.  This document defines a set of guidelines for applying
 restrictions of that type for Chinese, Japanese and Korean (CJK)
 scripts and the zones that use them and, perhaps, the beginning of a
 framework for thinking about other zones, languages, and scripts.

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
 2.  Definitions, Context, and Notation . . . . . . . . . . . . . .  5
     2.1.  Definitions and Context. . . . . . . . . . . . . . . . .  5
     2.2.  Notation for Ideographs and Other Non-ASCII CJK
           Characters . . . . . . . . . . . . . . . . . . . . . . .  9
 3.  Scope of the Administrative Guidelines . . . . . . . . . . . .  9
     3.1.  Principles Underlying These Guidelines . . . . . . . . . 10
     3.2.  Registration of IDL. . . . . . . . . . . . . . . . . . . 13
           3.2.1.  Using the Language Variant Table . . . . . . . . 13
           3.2.2.  IDL Package. . . . . . . . . . . . . . . . . . . 14
           3.2.3.  Procedure for Registering IDLs . . . . . . . . . 14
     3.3.  Deletion and Transfer of IDL and IDL Package . . . . . . 19
     3.4.  Activation and Deactivation of IDL Variants  . . . . . . 19
           3.4.1.  Activation Algorithm . . . . . . . . . . . . . . 19
           3.4.2.  Deactivation Algorithm . . . . . . . . . . . . . 20
     3.5.  Managing Changes in Language Associations. . . . . . . . 21
     3.6.  Managing Changes to Language Variant Tables. . . . . . . 21
 4.  Examples of Guideline Use in Zones . . . . . . . . . . . . . . 21
 5.  Syntax Description for the Language Variant Table. . . . . . . 25
     5.1.  ABNF Syntax. . . . . . . . . . . . . . . . . . . . . . . 25
     5.2.  Comments and Explanation of Syntax . . . . . . . . . . . 25
 6.  Security Considerations. . . . . . . . . . . . . . . . . . . . 27
 7.  Index to Terminology . . . . . . . . . . . . . . . . . . . . . 27
 8.  Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . 28
 9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
     9.1.  Normative References . . . . . . . . . . . . . . . . . . 29
     9.2.  Informative References . . . . . . . . . . . . . . . . . 30
 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 30
     10.1. Authors' Addresses . . . . . . . . . . . . . . . . . . . 31
     10.2. Editors' Addresses . . . . . . . . . . . . . . . . . . . 32
 11. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 33

Konishi, et al. Informational [Page 2] RFC 3743 JET Guidelines for IDN April 2004

1. Introduction

 Domain names form the fundamental naming architecture of the
 Internet.  Countless Internet protocols and applications rely on
 them, not just for stability and continuity, but also to avoid
 ambiguity.  They were designed to be identifiers without any language
 context.  However, as domain names have become visible to end users
 through Web URLs and e-mail addresses, the strings in domain-name
 labels are being increasingly interpreted as names, words, or
 phrases.  It is likely that users will do the same with languages of
 differing character sets, such as Chinese, Japanese and Korean (CJK),
 in which many words or concepts are represented using short sequences
 of characters.
 The introduction of what are called Internationalized Domain Names
 (IDN) amplifies both the difficulty of putting names into identifiers
 and the confusion that exists between scripts and languages.
 Character symbols that appear (or actually are) identical, or that
 have similar or identical semantics but that are assigned the
 different code points, further increase the potential for confusion.
 DNS internationalization also affects a number of Internet protocols
 and applications and creates additional layers of complexity in terms
 of technical administration and services.  Given the added
 complications of using a much broader range of characters than the
 original small ASCII subset, precautions are necessary in the
 deployment of IDNs in order to minimize confusion and fraud.
 The IETF IDN Working Group [IDN-WG] addressed the problem of handling
 the encoding and decoding of Unicode strings into and out of Domain
 Name System (DNS) labels with the goal that its solution would not
 put the operational DNS at any risk.  Its work resulted in one
 primary protocol and three supporting ones, respectively:
    1. Internationalizing Host Names in Applications [IDNA]
    2. Preparation of Internationalized Strings [STRINGPREP]
    3. A Stringprep Profile for Internationalized Domain Names
       [NAMEPREP]
    4. Punycode [PUNYCODE]
 IDNA, which calls on the others, normalizes and transforms strings
 that are intended to be used as IDNs.  In combination, the four
 provide the minimum functions required for internationalization, such
 as performing case mappings, eliminating character differences that
 would cause severe problems, and specifying matching (equality).
 They also convert between the resulting Unicode code points and an
 ASCII-based form that is more suitable for storing in actual DNS
 labels.  In this way, the IDNA transformations improve a user's
 chances of getting to the correct IDN.

Konishi, et al. Informational [Page 3] RFC 3743 JET Guidelines for IDN April 2004

 Addressing the issues around differing character sets, a primary
 consideration and administrative challenge involves region-specific
 definitions, interpretations, and the semantics of strings to be used
 in IDNs.  A Unicode string may have a specific meaning as a name,
 word, or phrase in a particular language but that meaning could vary
 depending on the country, region, culture, or other context in which
 the string is used.  It might also have different interpretations in
 different languages that share some or all of the same characters.
 Therefore, individual zones and zone administrators may find it
 necessary to impose restrictions and procedures to reduce the
 likelihood of confusion, and instabilities of reference, within their
 own environments.
 Over the centuries, the evolution of CJK characters, and the
 differences in their use in different languages and even in different
 regions where the same language is spoken, has given rise to the idea
 of "variants", wherein one conceptual character can be identified
 with several different Code Points in character sets for computer
 use.  This document provides a framework for handling such variants
 while minimizing the possibility of serious user confusion in the
 obtaining or using of domain names.  However, the concept of variants
 is complex and may require many different layers of solutions. This
 guideline offers only one of those solution components.  It is not
 sufficient by itself to solve the whole problem, even with zone-
 specific tables as described below.
 Additionally, because of local language or writing-system
 differences, it is impossible to create universally accepted
 definitions for which potential variants are the same and which are
 not the same.  It is even more difficult to define a technical
 algorithm to generate variants that are linguistically accurate.
 That is, that the variant forms produced make as much sense in the
 language as the originally specified forms.  It is also possible that
 variants generated may have no meaning in the associated language or
 languages.  The intention is not to generate meaningful "words" but
 to generate similar variants to be reserved.  So even though the
 method described in this document may not always be linguistically
 accurate, nor does it need to be, it increases the chances of getting
 the right variants while accepting the inherent limitations of the
 DNS and the complexities of human language.
 This document outlines a model for such conventions for zones in
 which labels that contain CJK characters are to be registered and a
 system for implementing that model.  It provides a mechanism that
 allows each zone to define its own local rules for permitted
 characters and sequences and the handling of IDNs and their variants.

Konishi, et al. Informational [Page 4] RFC 3743 JET Guidelines for IDN April 2004

 The document is an effort of the Joint Engineering Team (JET), a
 group composed of members of CNNIC, TWNIC, KRNIC, and JPNIC as well
 as other individual experts.  It offers guidelines for zone
 administrators, including but not limited to registry operators and
 registrars and information for all domain names holders on the
 administration of domain names that contain characters drawn from
 Chinese, Japanese, and Korean scripts.  Other language groups are
 encouraged to develop their own guidelines as needed, based on these
 guidelines if that is helpful.

2. Definitions, Context, and Notation

2.1. Definitions and Context

 This document uses a number of special terms.  In this section,
 definitions and explanations are grouped topically.  Some readers may
 prefer to skip over this material, returning, perhaps via the index
 to terminology in section 7, when needed.

2.1.1. IDN

 IDN: The term "IDN" has a number of different uses: (a) as an
 abbreviation for "Internationalized Domain Name"; (b) as a fully
 qualified domain name that contains at least one label that contains
 characters not appearing in ASCII, specifically not in the subset of
 ASCII recommended for domain names (the so-called "hostname" or "LDH"
 subset, see RFC1035 [STD13]); (c) as a label of a domain name that
 contains at least one character beyond ASCII; (d) as a Unicode string
 to be processed by Nameprep; (e) as a string that is an output from
 Nameprep; (f) as a string that is the result of processing through
 both Nameprep and conversion into Punycode; (g) as the abbreviation
 of an IDN (more properly, IDL) Package, in the terminology of this
 document; (h) as the abbreviation of the IETF IDN Working Group; (g)
 as the abbreviation of the ICANN IDN Committee; and (h) as standing
 for other IDN activities in other companies/organizations.
 Because of the potential confusion, this document uses the term "IDN"
 as an abbreviation for Internationalized Domain Name and,
 specifically, in the second sense described in (b) above.  It uses
 "IDL," defined immediately below, to refer to Internationalized
 Domain Labels.

2.1.2. IDL

 IDL: This document provides a guideline to be applied on a per-zone
 basis, one label at a time.  Therefore, the term "Internationalized
 Domain Label" or "IDL" will be used instead of the more general term
 "IDN" or its equivalents.  The processing specifications of this

Konishi, et al. Informational [Page 5] RFC 3743 JET Guidelines for IDN April 2004

 document may be applied, in some zones, to ASCII characters also, if
 those characters are specified as valid in a Language Variant Table
 (see below).  Hence, in some zones, an IDL may contain or consist
 entirely of "LDH" characters.

2.1.3. FQDN

 FQDN: A fully qualified domain name, one that explicitly contains all
 labels, including a Top-Level Domain (TLD) name.  In this context, a
 TLD name is one whose label appears in a nameserver record in the
 root zone.  The term "Domain Name Label" refers to any label of a
 FQDN.

2.1.4. Registrations

 Registration: In this document, the term "registration" refers to the
 process by which a potential domain name holder requests that a label
 be placed in the DNS either as an individual name within a domain or
 as a subdomain delegation from another domain name holder.  In the
 case of a successful registration, the label or delegation records
 are placed in the relevant zone file, or, more specifically, they are
 "activated" or made "active" and additional IDLs may be reserved as
 part of an "IDL Package" (see below).  The guidelines presented here
 are recommended for all zones, at any hierarchy level, in which CJK
 characters are to appear and not just domains at the first or second
 level.

2.1.5. RFC3066

 RFC3066: A system, widely used in the Internet, for coding and
 representing names of languages [RFC3066].  It is based on an
 International Organization for Standardization (ISO) standard for
 coding language names [ISO639], but expands it to provide additional
 precision.

2.1.6. ISO/IEC 10646

 ISO/IEC 10646: The international standard universal multiple-octet
 coded character set ("UCS") [IS10646].  The Code Point definitions of
 this standard are identical to those of corresponding versions of the
 Unicode standard (see below).  Consequently, the characters and their
 coding are often referred to as "Unicode characters."

2.1.7. Unicode Character

 Unicode Character: The term "Unicode character" is used here in
 reference to characters chosen from the Unicode Standard Version 3.2
 [UNICODE] (and hence from ISO/IEC 10646).  In this document, the

Konishi, et al. Informational [Page 6] RFC 3743 JET Guidelines for IDN April 2004

 characters are identified by their positions, or "Code Points." The
 notation U+12AB, for example, indicates the character at the position
 12AB (hexadecimal) in the Unicode 3.2 table.  For characters in
 positions above FFFF, i.e., requiring more than sixteen bits to
 represent, a five to eight-character string is used, such as U+112AB
 for the character in position 12AB of plane 1.

2.1.8. Unicode String

 Unicode String: "Unicode string" refers to a string of Unicode
 characters.  The Unicode string is identified by the sequence of the
 Unicode characters regardless of the encoding scheme.

2.1.9. CJK Characters

 CJK Characters: CJK characters are characters commonly used in the
 Chinese, Japanese, or Korean languages, including but not limited to
 those defined in the Unicode Standard as ASCII (U+0020 to U+007F),
 Han ideographs (U+3400 to U+9FAF and U+20000 to U+2A6DF), Bopomofo
 (U+3100 to U+312F and U+31A0 to U+31BF), Kana (U+3040 to U+30FF),
 Jamo (U+1100 to 11FF and U+3130 to U+318F), Hangul (U+AC00 to U+D7AF
 and U+3130 to U+318F), and the respective compatibility forms.  The
 particular characters that are permitted in a given zone are
 specified in the Language Variant Table(s) for that zone.

2.1.10. Label String

 Label String: A generic term referring to a string of characters that
 is a candidate for registration in the DNS or such a string, once
 registered.  A label string may or may not be valid according to the
 rules of this specification and may even be invalid for IDNA use.
 The term "label", by itself, refers to a string that has been
 validated and may be formatted to appear in a DNS zone file.

2.1.11. Language Variant Table

 Language Variant Table: The key mechanisms of this specification
 utilize a three-column table, called a Language Variant Table, for
 each language permitted to be registered in the zone.  Those columns
 are known, respectively, as "Valid Code Point", "Preferred Variant",
 and "Character Variant", which are defined separately below.  The
 Language Variant Tables are critical to the success of the guideline
 described in this document.  However, the principles to be used to
 generate the tables are not within the scope of this document and
 should be worked out by each registry separately (perhaps by adopting
 or adapting the work of some other registry).  In this document,
 "Table" and "Variant Table" are used as short forms for Language
 Variant Table.

Konishi, et al. Informational [Page 7] RFC 3743 JET Guidelines for IDN April 2004

2.1.12. Valid Code Point

 Valid Code Point: In a Language Variant Table, the list of Code
 Points that is permitted for that language.  Any other Code Points,
 or any string containing them, will be rejected by this
 specification.  The Valid Code Point list appears as the first column
 of the Language Variant Table.

2.1.13. Preferred Variant

 Preferred Variant: In a Language Variant Table, a list of Code Points
 corresponding to each Valid Code Point and providing possible
 substitutions for it.  These substitutions are "preferred" in the
 sense that the variant labels generated using them are normally
 registered in the zone file, or "activated."  The Preferred Code
 Points appear in column 2 of the Language Variant Table.  "Preferred
 Code Point" is used interchangeably with this term.

2.1.14. Character Variant

 Character Variant: In a Language Variant Table, a second list of Code
 Points corresponding to each Valid Code Point and providing possible
 substitutions for it.  Unlike the Preferred Variants, substitutions
 based on Character Variants are normally reserved but not actually
 registered (or "activated").  Character Variants appear in column 3
 of the Language Variant Table.  The term "Code Point Variants" is
 used interchangeably with this term.

2.1.15. Preferred Variant Label

 Preferred Variant Label: A label generated by use of Preferred
 Variants (or Preferred Code Points).

2.1.16. Character Variant Label

 Character Variant Label: A label generated by use of Character
 Variants.

2.1.17. Zone Variant

 Zone Variant: A Preferred or Character Variant Label that is actually
 to be entered (registered) into the DNS.  That is, into the zone file
 for the relevant zone.  Zone Variants are also referred to as Zone
 Variant Labels or Active (or Activated) Labels.

Konishi, et al. Informational [Page 8] RFC 3743 JET Guidelines for IDN April 2004

2.1.18. IDL Package

 IDL Package: A collection of IDLs as determined by these Guidelines.
 All labels in the package are "reserved", meaning they cannot be
 registered by anyone other than the holder of the Package.  These
 reserved IDLs may be "activated", meaning they are actually entered
 into a zone file as a "Zone Variant".  The IDL Package also contains
 identification of the language(s) associated with the registration
 process.  The IDL and its variant labels form a single, atomic unit.

2.2. Notation for Ideographs and Other Non-ASCII CJK Characters.

 For purposes of clarity, particularly in regard to examples, Han
 ideographs appear in several places in this document.  However, they
 do not appear in the ASCII version of this document.  For the
 convenience of readers of the ASCII version, and some readers not
 familiar with recognizing and distinguishing Chinese characters, most
 uses of these characters will be associated with both their Unicode
 Code Points and an "asterisk tag" with its corresponding Chinese
 Romanization [ISO7098], with the tone mark represented by a number
 from 1 to 4.  Those tags have no meaning outside this document; they
 are a quick visual and reading reference to help facilitate the
 combinations and transformations of characters in the guideline and
 table excerpts.

3. Scope of the Administrative Guidelines

 Zone administrators are responsible for the administration of the
 domain name labels under their control.  A zone administrator might
 be responsible for a large zone, such as a top-level domain (TLD),
 whether generic or country code, or a smaller one, such as a typical
 second- or third-level domain.  A large zone is often more complex
 than its smaller counterpart.  However, actual technical
 administrative tasks, such as addition, deletion, delegation, and
 transfer of zones between domain name holders, are similar for all
 zones.
 This document provides guidelines for the ways CJK characters should
 be handled within a zone, for how language issues should be
 considered and incorporated, and for how Domain Name Labels
 containing CJK characters should be administered (including
 registration, deletion, and transfer of labels).
 Other IDN policies, such as the creation of new top-level domains
 (TLDs), the cost structure for registrations, and how the processes
 described here get allocated between registrar and registry if the
 zone makes that distinction, also are outside the scope of this
 document.

Konishi, et al. Informational [Page 9] RFC 3743 JET Guidelines for IDN April 2004

 Technical implementation issues are not discussed here either.  For
 example, deciding which guidelines should be implemented as registry
 actions and which should be registrar actions is left to zone
 administrators, with the possibility that it will differ from zone to
 zone.

3.1. Principles Underlying These Guidelines

 In many places, in the event of a dispute over rights to a name (or,
 more accurately, DNS label string), this document assumes "first-
 come, first-served" (FCFS) as a resolution policy even though FCFS is
 not listed below as one of the principles for this document.  If
 policies are already in place governing priorities and "rights", one
 can use the guidelines here by replacing uses of FCFS in this
 document with policies specific to the zone.  Some of the guidelines
 here may not be applicable to other policies for determining rights
 to labels.  Still other alternatives, such as use of UDRP [UDRP] or
 mutual exclusion, might have little impact on other aspects of these
 guidelines.
 (a) Although some Unicode strings may be pure identifiers made up of
 an assortment of characters from many languages and scripts, IDLs are
 likely to be "words" or "names" or "phrases" that have specific
 meaning in a language.  While a zone administration might or might
 not require "meaning" as a registration criterion, meaning could
 prove to be a useful tool for avoiding user confusion.
    Each IDL to be registered should be associated administratively
    with one or more languages.
 Language associations should either be predetermined by the zone
 administrator and applied to the entire zone or be chosen by the
 registrants on a per-IDL basis.  The latter may be necessary for some
 zones, but it will make administration more difficult and will
 increase the likelihood of conflicts in variant forms.
 A given zone might have multiple languages associated with it or it
 may have no language specified at all.  Omitting specification of a
 language may provide additional opportunities for user confusion and
 is therefore NOT recommended.
 (b) Each language uses only a subset of Unicode characters.
 Therefore, if an IDL is associated with a language, it is not
 permitted to contain any Unicode character that is not within the
 valid subset for that language.
    Each IDL to be registered must be verified against the valid
    subset of Unicode for the language(s) associated with the IDL.

Konishi, et al. Informational [Page 10] RFC 3743 JET Guidelines for IDN April 2004

    That subset is specified by the list of characters appearing in
    the first column of the language and zone-specific tables as
    described later in this document.
 If the IDL fails this test for any of its associated languages, the
 IDL is not valid for registration.
 Note that this verification is not necessarily linguistically
 accurate, because some languages have special rules.  For example,
 some languages impose restrictions on the order in which particular
 combinations of characters may appear.  Characters that are valid for
 the language, and hence permitted by this specification, might still
 not form valid words or even strings in the language.
 (c) When an IDL is associated with a language, it may have Character
 Variants that depend on that language associated with it in addition
 to any Preferred Variants.  These variants are potential sources of
 confusion with the Code Points in the original label string.
 Consequently, the labels generated from them should be unavailable to
 registrants of other names, words, or phrases.
    During registration, all labels generated from the Character
    Variants for the associated language(s) of the IDL should be
    reserved.
 IDL reservations of the type described here normally do not appear in
 the distributed DNS zone file.  In other words, these reserved IDLs
 may not resolve.  Domain name holders could request that these
 reserved IDLs be placed in the zone file and made active and
 resolvable.
 Zones will need to establish local policies about how they are to be
 made active.  Specifically, many zones, especially at the top level,
 have prohibited or restricted the use of "CNAME"s DNS aliases,
 especially CNAMEs that point to nameserver delegation records (NS
 records).  And long-term use of long-term aliases for domain
 hierarchies, rather than single names ("DNAME records") are
 considered problematic because of the recursion they can introduce
 into DNS lookups.
 (d) When an IDL is a "name", "word", or "phrase", it will have
 Character Variants depending on the associated language.
 Furthermore, one or more of those Character Variants will be used
 more often than others for linguistic, political, or other reasons.
 These more commonly used variants are distinguished from ordinary
 Character Variants and are known as Preferred Variant(s) for the
 particular language.

Konishi, et al. Informational [Page 11] RFC 3743 JET Guidelines for IDN April 2004

    To increase the likelihood of correct and predictable resolution
    of the IDN by end users, all labels generated from the Preferred
    Variants for the associated language(s) should be resolvable.
 In other words, the Preferred Variant Labels should appear in the
 distributed DNS zone file.
 (e) IDLs associated with one or more languages may have a large
 number of Character Variant Labels or Preferred Variant Labels.  Some
 of these labels may include combinations of characters that are
 meaningless or invalid linguistically.  It may therefore be
 appropriate for a zone to adopt procedures that include only
 linguistically acceptable labels in the IDL Package.
    A zone administrator may impose additional rules and other
    processing activities to limit the number of Character Variant
    Labels or Preferred Variant Labels that are actually reserved or
    registered.
 These additional rules and other processing activities are based on
 policies and/or procedures imposed on a per-zone basis and therefore
 are not within the scope of this document.  Such policies or
 procedures might be used, for example, to restrict the number of
 Preferred Variant Labels actually reserved or to prevent certain
 words from being registered at all.
 (f) There are some Character Variant Labels and Preferred Variant
 Labels that are associated with each IDL.  These labels are
 considered "equivalent" to each another.  To avoid confusion, they
 all should be assigned to a single domain name holder.
    The IDL and its variant labels should be grouped together into a
    single atomic unit, known in this document as an "IDL Package".
 The IDL Package is created upon registration and is atomic: Transfer
 and deletion of an IDL is performed on the IDL Package as a whole.
 That is, an IDL within the IDL Package may not be transferred or
 deleted individually; any re-registration, transfers, or other
 actions that impact the IDL should also affect the other variants.
 The name-conflict resolution policy associated with this zone could
 result in a conflict with the principle of IDL Package atomicity.  In
 such a case, the policy must be defined to make the precedence clear.

Konishi, et al. Informational [Page 12] RFC 3743 JET Guidelines for IDN April 2004

3.2. Registration of IDL

 To conform to the principles described in 3.1, this document
 introduces two concepts: the Language Variant Table and the IDL
 Package.  These are described in the next two subsections, followed
 by a description of the algorithm that is used to interpret the table
 and generate variant labels.

3.2.1. Using the Language Variant Table

 For each zone that uses a given language, each language should have
 its own Language Variant Table.  The table consists of a header
 section that identifies references and version information, followed
 by a section with one row for each Code Point that is valid for the
 language and three columns.
    (1) The first column contains the subset of Unicode characters
        that is valid to be registered ("Valid Code Point").  This is
        used to verify the IDL to be registered (see 3.1b).  As in the
        registration procedure described later, this column is used as
        an index to examine characters that appear in a proposed IDL
        to be processed.  The collection of Valid Code Points in the
        table for a particular language can be thought of as defining
        the script for that language, although the normal definition
        of a script would not include, for example, ASCII characters
        with CJK ones.
    (2) The second column contains the Preferred Variant(s) of the
        corresponding Unicode character in column one ("Valid Code
        Point").  These variant characters are used to generate the
        Preferred Variant Labels for the IDL.  Those labels should be
        resolvable (see 3.1d).  Under normal circumstances, all of
        those Preferred Variant Labels will be activated in the
        relevant zone file so that they will resolve when the DNS is
        queried for them.
    (3) The third column contains the Character Variant(s) for the
        corresponding Valid Code Point.  These are used to generate
        the Character Variant Labels of the IDL, which are then to be
        reserved (see 3.1c).  Registration, or activation, of labels
        generated from Character Variants will normally be a
        registrant decision, subject to local policy.
 Each entry in a column consists of one or more Code Points, expressed
 as a numeric character number in the Unicode table and optionally
 followed by a parenthetical reference.  The first column, or Valid
 Code Point, may have only one Code Point specified in a given row.
 The other columns may have more than one.

Konishi, et al. Informational [Page 13] RFC 3743 JET Guidelines for IDN April 2004

 Any row may be terminated with an optional comment, starting with
 "#".
 The formal syntax of the table and more-precise definitions of some
 of its organization appear in Section 5.
 The Language Variant Table should be provided by a relevant group,
 organization, or body.  However, the question of who is relevant or
 has the authority to create this table and the rules that define it
 is beyond the scope of this document.

3.2.2. IDL Package

 The IDL Package is created on successful registration and consists
 of:
    (1) the IDL registered
    (2) the language(s) associated with the IDL
    (3) the version of the associated character variant table
    (4) the reserved IDLs
    (5) active IDLs, that is, "Zone Variant Labels" that are to appear
        in the DNS zone file

3.2.3. Procedure for Registering IDLs

 An explanation follows each step.
 Step 1.    IN <= IDL to be registered and
            {L} <= Set of languages associated with IN
 Start the process with the label string (prospective IDL) to be
 registered and the associated language(s) as input.
 Step 2.    Generate the Nameprep-processed version of the IN,
            applying all mappings and canonicalization required by
            IDNA.
 The prospective IDL is processed by using Nameprep to apply the
 normalizations and exclusions globally required to use IDNA.  If the
 Nameprep processing fails, then the IDL is invalid and the
 registration process must stop.

Konishi, et al. Informational [Page 14] RFC 3743 JET Guidelines for IDN April 2004

 Step 2.1.  NP(IN) <= Nameprep processed IN
 Step 2.2.  Check availability of NP(IN).  If not available, route to
            conflict policy.
 The Nameprep-processed IDL is then checked against the contents of
 the zone file and previously created IDL Packages.  If it is already
 registered or reserved, then a conflict exists that must be resolved
 by applying whatever policy is applicable for the zone.  For example,
 if FCFS is used, the registration process terminates unless the
 conflict resolution policy provides another alternative.
 Step 3.    Process each language.
            For each language (AL) in {L}
 Step 3 goes through all languages associated with the proposed IDL
 and checks each character (after Nameprep has been applied) for
 validity in each of them.  It then applies the Preferred Variants
 (column 2 values) and the Character Variants (column 3 values) to
 generate candidate labels.
 Step 3.1.  Check validity of NP(IN) in AL.  If failed, stop
            processing.
 In step 3.1, IDL validation is done by checking that every Code Point
 in the Nameprep-processed IDL is a Code Point allowed by the "Valid
 Code Point" column of the Character Variant Table for the language.
 This is then repeated for any other languages (and hence, Language
 Variant Tables) specified in the registration.  If one or more Code
 Points are not valid, the registration process terminates.
 Step 3.2.  PV(IN,AL) <= Set of available Nameprep-processed Preferred
                         Variants of NP(IN) in AL
 Step 3.2 generates the list of Preferred Variant Labels of the IDL by
 doing a combination (see Step 3.2A below) of all possible variants
 listed in the "Preferred Variant(s)" column for each Code Point in
 the Nameprep-processed IDL.  The generated Preferred Variant Labels
 must be processed through Nameprep.  If the Nameprep processing fails
 for any Preferred Variant Label (this is unlikely to occur if the
 Preferred Variants are processed through Nameprep before being placed
 in the table), then that variant label will be removed from the list.
 The remaining Preferred Variant Labels in the list are then checked
 to see whether they are already registered or reserved.  If any are
 registered or reserved, then the conflict resolution policy will
 apply.  In general, this will not prevent the originally requested
 IDL from being registered unless the policy prevents such
 registration.  For example, if FCFS is applied, then the conflicting
 variants will be removed from the list, but the originally requested

Konishi, et al. Informational [Page 15] RFC 3743 JET Guidelines for IDN April 2004

 IDL and any remaining variants will be registered (see steps 5 and 8
 below).
 Step 3.2A Generating variant labels from Variant Code Points.
 Steps 3.2 and 3.3 require that the Preferred Variants and Character
 Variants be combined with the original IDL to form sets of variant
 labels.  Conceptually, one starts with the original, Nameprep-
 processed, IDL and examines each of its characters in turn.  If a
 character is encountered for which there is a corresponding Preferred
 Variant or Character Variant, a new variant label is produced with
 the Variant Code Point substituted for the original one.  If variant
 labels already exist as the result of the processing of characters
 that appeared earlier in the original IDL, then the substitutions are
 made in them as well, resulting in additional generated variant
 labels.  This operation is repeated separately for the Preferred
 Variants (in Step 3.2) and Character Variants (in Step 3.3).  Of
 course, equivalent results could be achieved by processing the
 original IDL's characters in order, building the Preferred Variant
 Label set and Character Variant Label set in parallel.
 This process will sometimes generate a very large number of labels.
 For example, if only two of the characters in the original IDL are
 associated with Preferred Variants and if the first of those
 characters has three Preferred Variants and the second has two, one
 ends up with 12 variant labels to be placed in the IDL Package and,
 normally, in the zone file.  Repeating the process for Character
 Variants, if any exist, would further increase the number of labels.
 And if more than one language is specified for the original IDL, then
 repetition of the process for additional languages (see step 4,
 below) might further increase the size of the set.

Konishi, et al. Informational [Page 16] RFC 3743 JET Guidelines for IDN April 2004

 For illustrative purposes, the "combination" process could be
 achieved by a recursive function similar to the following pseudocode:
      Function Combination(Str)
        F <= first codepoint of Str
        SStr <= Substring of Str, without the first code point
        NSC <= {}
        If SStr is empty then
         for each V in (Variants of code point F)
           NSC = NSC set-union (the string with the code point V)
         End of Loop
        Else
          SubCom = Combination(SStr)
          For each V in (Variants of code point F)
            For each SC in SubCom
              NSC = NSC set-union (the string with the
                  first code point V followed by the string SC)
            End of Loop
          End of Loop
        Endif
        Return NSC
 Step 3.3.  CV(IN,AL) <= Set of available Nameprep-processed Character
                         Variants of NP(IN) in AL
 This step generates the list of Character Variant Labels by doing a
 combination (see Step 3.2A above) of all the possible variants listed
 in the "Character Variant(s)" column for each Code Point in the
 Nameprep-processed original IDL.  As with the Preferred Variant
 Labels, the generated Character Variant Labels must be processed by,
 and acceptable to, Nameprep.  If the Nameprep processing fails for a
 Character Variant Label, then that variant label will be removed from
 the list.  The remaining Character Variant Labels are then checked to
 be sure they are not registered or reserved.  If one or more are,
 then the conflict resolution policy is applied.  As with Preferred
 Variant Labels, a conflict that is resolved in favor of the earlier
 registrant does not, in general, prevent the IDL from being
 registered, nor the remaining variants from being reserved in step 6
 below.
 Step 3.4.  End of Loop

Konishi, et al. Informational [Page 17] RFC 3743 JET Guidelines for IDN April 2004

 Step 4.    Let PVall be the set-union of all PV(IN,AL)
 Step 4 generates the Preferred Variants Label for all languages.  In
 this step, and again in step 6 below, the zone administrator may
 impose additional rules and processing activities to restrict the
 number of Preferred (tentatively to be reserved and activated) and
 Character (tentatively to be reserved) Label Variants.  These
 additional rules and processing activities are zone policy specific
 and therefore are not specified in this document.
 Step 5.    {ZV} <= PVall set-union NP(IN)
 Step 5 generates the initial Zone Variants.  The set includes all
 Preferred Variants for all languages and the original Nameprep-
 processed IDL.  Unless excluded by further processing, these Zone
 Variants will be activated.  That is, placed into the DNS zone.  Note
 that the "set-union" operation will eliminate any duplicates.
 Step 6.    Let CVall be the set-union of all CV(IN,AL), set-minus
            {ZV}
 Step 6 generates the Reserved Label Variants (the Character Variant
 Label set).  These labels are normally reserved but not activated.
 The set includes all Character Variant Labels for all languages, but
 not the Zone Variants defined in the previous step.  The set-union
 and set-minus operations eliminate any duplicates.
 Step 7.    Create IDL Package for IN using IN, {L}, {ZV} and CVall
 In Step 7, the "IDL Package" is created using the original IDL, the
 associated language(s), the Zone Variant Labels, and the Reserved
 Variant Labels.  If zone-specific additional processing or filtering
 is to be applied to eliminate linguistically inappropriate or other
 forms, it should be applied before the IDL Package is actually
 assembled.
 Step 8.    Put {ZV} into zone file
 The activated IDLs are converted via ToASCII with UseSTD13ASCIIRules
 [IDNA] before being placed into the zone file.  This conversion
 results in the IDLs being in the actual IDNA ("Punycode") form used
 in zone files, while the IDLs have been carried in Unicode form up to
 this point.  If ToASCII fails for any of the activated IDLs, that IDL
 must not be placed into the zone file.  If the IDL is a subdomain
 name, it will be delegated.

Konishi, et al. Informational [Page 18] RFC 3743 JET Guidelines for IDN April 2004

3.3. Deletion and Transfer of IDL and IDL Package

 In traditional domain administration, every Domain Name Label is
 independent of all other Domain Name Labels.  Registration, deletion,
 and transfer of labels is done on a per-label basis.  However, with
 the guidelines discussed here, each IDL is associated with specific
 languages, with all label variants, both active (zone) and reserved,
 together in an IDL Package.  This quite deliberately prohibits labels
 that contain sufficient mixtures of characters from different scripts
 to make them impossible as words in any given language.  If a zone
 chooses to not impose that restriction--that is, to permit labels to
 be constructed by picking characters from several different languages
 and scripts--then the guidelines described here would be
 inappropriate.
 As stated earlier, the IDL package should be treated as a single
 atomic unit and all variants of the IDL should belong to a single
 domain-name holder.  If the local policy related to the handling of
 disagreements requires a particular IDL to be transferred and deleted
 independently of the IDL Package, the conflict policy would take
 precedence.  In such an event, the conflict policy should include a
 transfer or delete procedure that takes the nature of IDL Packages
 into consideration.
 When an IDL Package is deleted, all of the Zone and Reserved Label
 Variants again become available.  The deletion of one IDL Package
 does not change any other IDL Packages.

3.4. Activation and Deactivation of IDL variants

 Because there are active (registered) IDLs and inactive (reserved but
 not registered) IDLs within an IDL package, processes are required to
 activate or deactivate IDL variants within an IDL Package.

3.4.1. Activation Algorithm

 Step 1.  IN <= IDL to be activated and PA <= IDL Package
 Start with the IDL to be activated and the IDL Package of which it is
 a member.
 Step 2.  NP(IN) <= Nameprep processed IN
 Process the IDL through Nameprep.  This step should never cause a
 problem, or even a change, since all labels that become part of the
 IDL Package are processed through Nameprep in Step 3.2 or 3.3 of the
 Registration procedure (section 3.2.3).

Konishi, et al. Informational [Page 19] RFC 3743 JET Guidelines for IDN April 2004

 Step 3.  If NP(IN) not in CVall then stop
 Verify that the Nameprep-processed version of the IDL appears as a
 still-unactivated label in the IDL Package, i.e., in the list of
 Reserved Label Variants, CVall.  It might be a useful "sanity check"
 to also verify that it does not already appear in the zone file.
 Step 4. CVall <= CVall set-minus NP(IN) and {ZV} <= {ZV} set-union
         NP(IN)
 Within the IDL Package, remove the Nameprep-processed version of the
 IDL from the list of Reserved Label Variants and add it to the list
 of active (zone) label variants.
 Step 5.  Put {ZV} into the zone file
 Actually register (activate) the Zone Variant Labels.

3.4.2. Deactivation Algorithm

 Step 1.  IN <= IDL to be deactivated and PA <= IDL Package
 As with activation, start with the IDL to be deactivated and the IDL
 Package of which it is a member.
 Step 2.  NP(IN) <= Nameprep processed IN
 Get the Nameprep-processed version of the name (see discussion in the
 previous section).
 Step 3.  If NP(IN) not in {ZV} then stop
 Verify that the Nameprep-processed version of the IDL appears as an
 activated (zone) label variant in the IDL Package.  It might be a
 useful "sanity check" at this point to also verify that it actually
 appears in the zone file.
 Step 4. CVall <= CVall set-union NP(IN) and {ZV} <= {ZV} set-minus
         NP(IN)
 Within the IDL Package, remove the Nameprep-processed version of the
 IDL from the list of Active (Zone) Label Variants and add it to the
 list of Reserved (but inactive) Label Variants.
 Step 5.  Put {ZV} into the zone file

Konishi, et al. Informational [Page 20] RFC 3743 JET Guidelines for IDN April 2004

3.5. Managing Changes in Language Associations

 Since the IDL package is an atomic unit and the associated list of
 variants must not be changed after creation, this document does not
 include a mechanism for adding and deleting language associations
 within the IDL package.  Instead, it recommends deleting the IDL
 package entirely, followed by a registration with the new set of
 languages.  Zone administrators may find it desirable to devise
 procedures that prevent other parties from capturing the labels in
 the IDL Package during these operations.

3.6. Managing Changes to the Language Variant Tables

 Language Variant Tables are subject to changes over time, and these
 changes may or may not be backward compatible.  It is possible that
 updated Language Variant Tables may produce a different set of
 Preferred Variants and Reserved Variants.
 In order to preserve the atomicity of the IDL Package, when the
 Language Variant Table is changed, IDL Packages created using the
 previous version of the Language Variant Table must not be updated or
 affected.

4. Examples of Guideline Use in Zones

 To provide a meaningful example, some Language Variant Tables must be
 defined.  Assume, then, for the purpose of giving examples, that the
 following four Language Variant Tables are defined:
 Note: these tables are not a representation of the actual tables, and
 they do not contain sufficient entries to be used in any actual
 implementation.  IANA maintains a voluntary registry of actual tables
 [IANA-LVTABLES] which may be consulted for complete examples.
 a) Language Variant Table for zh-cn and zh-sg

Reference 1 CP936 (commonly known as GBK) Reference 2 zVariant, zTradVariant, zSimpVariant in Unihan.txt [UNIHAN] Reference 3 List of Simplified character Table (Simplified column) Reference 4 zSimpVariant in Unihan.txt [UNIHAN] Reference 5 variant that exists in GB2312, common simplified hanzi

 Version 1 20020701 # July 2002
 56E2(1);56E2(5);5718(2)           # sphere, ball, circle; mass, lump
 5718(1);56E2(4);56E2(2),56E3(2)   # sphere, ball, circle; mass, lump
 60F3(1);60F3(5);                  # think, speculate, plan, consider
 654E(1);6559(5);6559(2)           # teach

Konishi, et al. Informational [Page 21] RFC 3743 JET Guidelines for IDN April 2004

 6559(1);6559(5);654E(2)           # teach, class
 6DF8(1);6E05(5);6E05(2)           # clear
 6E05(1);6E05(5);6DF8(2)           # clear, pure, clean; peaceful
 771E(1);771F(5);771F(2)           # real, actual, true, genuine
 771F(1);771F(5);771E(2)           # real, actual, true, genuine
 8054(1);8054(3);806F(2)           # connect, join; associate, ally
 806F(1);8054(3);8054(2),8068(2)   # connect, join; associate, ally
 96C6(1);96C6(5);                  # assemble, collect together
 b) Language Variant Table for zh-tw
 Reference 1 CP950 (commonly known as BIG5)
 Reference 2 zVariant, zTradVariant, zSimpVariant in Unihan.txt
 Reference 3 List of Simplified Character Table (Traditional column)
 Reference 4 zTradVariant in Unihan.txt
 Version 1 20020701 # July 2002
 5718(1);5718(4);56E2(2),56E3(2)   # sphere, ball, circle; mass, lump
 60F3(1);60F3(1);                  # think, speculate, plan, consider
 6559(1);6559(1);654E(2)           # teach, class
 6E05(1);6E05(1);6DF8(2)           # clear, pure, clean; peaceful
 771F(1);771F(1);771E(2)           # real, actual, true, genuine
 806F(1);806F(3);8054(2),8068(2)   # connect, join; associate, ally
 96C6(1);96C6(1);                  # assemble, collect together
 c) Language Variant Table for ja
 Reference 1 CP932 (commonly known as Shift-JIS)
 Reference 2 zVariant in Unihan.txt
 Reference 3 variant that exists in JIS X0208, commonly used Kanji
 Version 1 20020701 # July 2002
 5718(1);5718(3);56E3(2)           # sphere, ball, circle; mass, lump
 60F3(1);60F3(3);                  # think, speculate, plan, consider
 654E(1);6559(3);6559(2)           # teach
 6559(1);6559(3);654E(2)           # teach, class
 6DF8(1);6E05(3);6E05(2)           # clear
 6E05(1);6E05(3);6DF8(2)           # clear, pure, clean; peaceful
 771E(1);771E(1);771F(2)           # real, actual, true, genuine
 771F(1);771F(1);771E(2)           # real, actual, true, genuine
 806F(1);806F(1);8068(2)           # connect, join; associate, ally
 96C6(1);96C6(3);                  # assemble, collect together
 d) Language Variant Table for ko
 Reference 1 CP949 (commonly known as EUC-KR)

Konishi, et al. Informational [Page 22] RFC 3743 JET Guidelines for IDN April 2004

 Reference 2 zVariant and K-source in Unihan.txt
 Version 1 20020701 # July 2002
 5718(1);5718(1);56E3(2)           # sphere, ball, circle; mass, lump
 60F3(1);60F3(1);                  # think, speculate, plan, consider
 654E(1);654E(1);6559(2)           # teach
 6DF8(1);6DF8(1);6E05(2)           # clear
 771E(1);771E(1);771F(2)           # real, actual, true, genuine
 806F(1);806F(1);8068(2)           # connect, join; associate, ally
 96C6(1);96C6(1);                  # assemble, collect together
 Example 1: IDL = (U+6E05 U+771F U+6559) *qing2 zhen1 jiao4*
            {L} = {zh-cn, zh-sg, zh-tw}
 NP(IN) = (U+6E05 U+771F U+6559)
 PV(IN,zh-cn) = (U+6E05 U+771F U+6559)
 PV(IN,zh-sg) = (U+6E05 U+771F U+6559)
 PV(IN,zh-tw) = (U+6E05 U+771F U+6559)
 {ZV} = {(U+6E05 U+771F U+6559)}
 CVall = {(U+6E05 U+771E U+6559),
         (U+6E05 U+771E U+654E),
         (U+6E05 U+771F U+654E),
         (U+6DF8 U+771E U+6559),
         (U+6DF8 U+771E U+654E),
         (U+6DF8 U+771F U+6559),
         (U+6DF8 U+771F U+654E)}
 Example 2: IDL = (U+6E05 U+771F U+6559) *qing2 zhen1 jiao4*
            {L} = {ja}
 NP(IN) = (U+6E05 U+771F U+6559)
 PV(IN,ja) = (U+6E05 U+771F U+6559)
 {ZV} = {(U+6E05 U+771F U+6559)}
 CVall = {(U+6E05 U+771E U+6559),
         (U+6E05 U+771E U+654E),
         (U+6E05 U+771F U+654E),
         (U+6DF8 U+771E U+6559),
         (U+6DF8 U+771E U+654E),
         (U+6DF8 U+771F U+6559),
         (U+6DF8 U+771F U+654E)}
 Example 3: IDL = (U+6E05 U+771F U+6559) *qing2 zhen1 jiao4*
            {L} = {zh-cn, zh-sg, zh-tw, ja, ko}
 NP(IN) = (U+6E05 U+771F U+6559) *qing2 zhen1 jiao4*

Konishi, et al. Informational [Page 23] RFC 3743 JET Guidelines for IDN April 2004

 Invalid registration because U+6E05 is invalid in L = ko
 Example 4: IDL = (U+806F U+60F3 U+96C6 U+5718)
                  *lian2 xiang3 ji2 tuan2*
           {L} = {zh-cn, zh-sg, zh-tw}
 NP(IN) = (U+806F U+60F3 U+96C6 U+5718)
 PV(IN,zh-cn) = (U+8054 U+60F3 U+96C6 U+56E2)
 PV(IN,zh-sg) = (U+8054 U+60F3 U+96C6 U+56E2)
 PV(IN,zh-tw) = (U+806F U+60F3 U+96C6 U+5718)
 {ZV} = {(U+8054 U+60F3 U+96C6 U+56E2),
        (U+806F U+60F3 U+96C6 U+5718)}
 CVall = {(U+8054 U+60F3 U+96C6 U+56E3),
         (U+8054 U+60F3 U+96C6 U+5718),
         (U+806F U+60F3 U+96C6 U+56E2),
         (U+806f U+60F3 U+96C6 U+56E3),
         (U+8068 U+60F3 U+96C6 U+56E2),
         (U+8068 U+60F3 U+96C6 U+56E3),
         (U+8068 U+60F3 U+96C6 U+5718)
 Example 5: IDL = (U+8054 U+60F3 U+96C6 U+56E2)
                *lian2 xiang3 ji2 tuan2*
           {L} = {zh-cn, zh-sg}
 NP(IN) = (U+8054 U+60F3 U+96C6 U+56E2)
 PV(IN,zh-cn) = (U+8054 U+60F3 U+96C6 U+56E2)
 PV(IN,zh-sg) = (U+8054 U+60F3 U+96C6 U+56E2)
 {ZV} = {(U+8054 U+60F3 U+96C6 U+56E2)}
 CVall = {(U+8054 U+60F3 U+96C6 U+56E3),
         (U+8054 U+60F3 U+96C6 U+5718),
         (U+806F U+60F3 U+96C6 U+56E2),
         (U+806f U+60F3 U+96C6 U+56E3),
         (U+806F U+60F3 U+96C6 U+5718),
         (U+8068 U+60F3 U+96C6 U+56E2),
         (U+8068 U+60F3 U+96C6 U+56E3),
         (U+8068 U+60F3 U+96C6 U+5718)}
 Example 6: IDL = (U+8054 U+60F3 U+96C6 U+56E2)
                *lian2 xiang3 ji2 tuan2*
            {L} = {zh-cn, zh-sg, zh-tw}
 NP(IN) = (U+8054 U+60F3 U+96C6 U+56E2)
 Invalid registration because U+8054 is invalid in L = zh-tw
 Example 7: IDL = (U+806F U+60F3 U+96C6 U+5718)
                *lian2 xiang3 ji2 tuan2*
            {L} = {ja,ko}

Konishi, et al. Informational [Page 24] RFC 3743 JET Guidelines for IDN April 2004

 NP(IN) = (U+806F U+60F3 U+96C6 U+5718)
 PV(IN,ja) = (U+806F U+60F3 U+96C6 U+5718)
 PV(IN,ko) = (U+806F U+60F3 U+96C6 U+5718)
 {ZV} = {(U+806F U+60F3 U+96C6 U+5718)}
 CVall = {(U+806F U+60F3 U+96C6 U+56E3),
         (U+8068 U+60F3 U+96C6 U+5718),
         (U+8068 U+60F3 U+96C6 U+56E3)}

5. Syntax Description for the Language Variant Table

 The formal syntax for the Language Variant Table is as follows, using
 the IETF "ABNF" metalanguage [ABNF].  Some comments on this syntax
 appear immediately after it.

5.1. ABNF Syntax

LanguageVariantTable = 1*ReferenceLine VersionLine 1*EntryLine ReferenceLine = "Reference" SP RefNo SP RefDesciption [ Comment ] CRLF RefNo = 1*DIGIT RefDesciption = *[VCHAR] VersionLine = "Version" SP VersionNo SP VersionDate [ Comment ] CRLF VersionNo = 1*DIGIT VersionDate = YYYYMMDD EntryLine = VariantEntry/Comment CRLF

VariantEntry = ValidCodePoint ";"

             PreferredVariant ";" CharacterVariant [ Comment ]

ValidCodePoint = CodePoint RefList = RefNo 0*( "," RefNo ) PreferredVariant = CodePointSet 0*( "," CodePointSet ) CharacterVariant = CodePointSet 0*( "," CodePointSet ) CodePointSet = CodePoint 0*( SP CodePoint ) CodePoint = 4*8DIGIT [ "(" Reflist ")" ] Comment = "#" *VCHAR

 YYYYMMDD is an integer, in alphabetic form, representing a date,
 where YYYY is the 4-digit year, MM is the 2-digit month, and DD is
 the 2-digit day.

5.2. Comments and Explanation of Syntax

 Any lines starting with, or portions of lines after, the hash
 symbol("#") are treated as comments.  Comments have no significance
 in the processing of the tables; nor are there any syntax
 requirements between the hash symbol and the end of the line.  Blank
 lines in the tables are ignored completely.

Konishi, et al. Informational [Page 25] RFC 3743 JET Guidelines for IDN April 2004

 Every language should have its own Language Variant Table provided by
 a relevant group, organization, or other body.  That table will
 normally be based on some established standard or standards.  The
 group that defines a Language Variant Table should document
 references to the appropriate standards at the beginning of the
 table, tagged with the word "Reference" followed by an integer (the
 reference number) followed by the description of the reference.  For
 example:
 Reference 1 CP936 (commonly known as GBK)
 Reference 2 zVariant, zTradVariant, zSimpVariant in Unihan.txt
 Reference 3 List of Simplified Character Table (Simplified column)
 Reference 4 zSimpVariant in Unihan.txt
 Reference 5 Variant that exists in GB2312, common simplified Hanzi
 Each Language Variant Table must have a version number and its
 release date.  This is tagged with the word "Version" followed by an
 integer then followed by the date in the format YYYYMMDD, where YYYY
 is the 4-digit year, MM is the 2-digit month, and DD is the 2-digit
 day of the publication date of the table.
 Version 1 20020701     # July 2002 Version 1
 The table has three columns, separated by semicolons: "Valid Code
 Point"; "Preferred Variant(s)"; and "Character Variant(s)".
 The "Valid Code Point" is the subset of Unicode characters that are
 valid to be registered.
 There can be more than one Preferred Variant; hence there could be
 multiple entries in the "Preferred Variant(s)" column.  If the
 "Preferred Variant(s)" column is empty, then there is no
 corresponding Preferred Variant; in other words, the Preferred
 Variant is null, there is no corresponding preferred variant
 codepoint, and no processing to add labels for preferred variants
 occurs."  Unless local policy dictates otherwise, the procedures
 above will result in only those labels that reflect the valid code
 point being activated (registered) into the zone file.
 The "Character Variant(s)" column contains all Character Variants of
 the Code Point.  Since the Code Point is always a variant of itself,
 to avoid redundancy, the Code Point is assumed to be part of the
 "Character Variant(s)" and need not be repeated in the "Character
 Variant(s)" column.
 If the variant in the "Preferred Variant(s)" or the "Character
 Variant(s)" column is composed of a sequence of Code Points, then
 sequence of Code Points is listed separated by a space.

Konishi, et al. Informational [Page 26] RFC 3743 JET Guidelines for IDN April 2004

 If there are multiple variants in the "Preferred Variant(s)" or the
 "Character Variant(s)" column, then each variant is separated by a
 comma.
 Any Code Point listed in the "Preferred Variant(s)" column must be
 allowed by the rules for the relevant language to be registered.
 However, this is not a requirement for the entries in the "Character
 Variant(s)" column; it is possible that some of those entries may not
 be allowed to be registered.
 Every Code Point in the table should have a corresponding reference
 number (associated with the references) specified to justify the
 entry.  The reference number is placed in parentheses after the Code
 Point.  If there is more than one reference, then the numbers are
 placed within a single set of parentheses and separated by commas.

6. Security Considerations

 As discussed in the Introduction, substantially-unrestricted use of
 international (non-ASCII) characters in domain name labels may cause
 user confusion and invite various types of attacks.  In particular,
 in the case of CJK languages, an attacker has an opportunity to
 divert or confuse users as a result of different characters (or, more
 specifically, assigned code points) with identical or similar
 semantics.  These Guidelines provide a partial remedy for those risks
 by supplying a framework for prohibiting inappropriate characters
 from being registered at all and for permitting "variant" characters
 to be grouped together and reserved, so that they can only be
 registered in the DNS by the same owner.  However, the system it
 suggests is no better or worse than the per-zone and per-language
 tables whose format and use this document specifies.  Specific
 tables, and any additional local processing, will reflect per-zone
 decisions about the balance between risk and flexibility of
 registrations.   And, of course, errors in construction of those
 tables may significantly reduce the quality of protection provided.

7. Index to Terminology

 As a convenience to the reader, this section lists all of the special
 terminology used in this document, with a pointer to the section in
 which it is defined.
      Activated Label                 2.1.17
      Activation                      2.1.4
      Active Label                    2.1.17
      Character Variant               2.1.14
      Character Variant Label         2.1.16
      CJK Characters                  2.1.9

Konishi, et al. Informational [Page 27] RFC 3743 JET Guidelines for IDN April 2004

      Code point                      2.1.7
      Code Point Variant              2.1.14
      FQDN                            2.1.3
      Hostname                        2.1.1
      IDL                             2.1.2
      IDL Package                     2.1.18
      IDN                             2.1.1
      Internationalized Domain Label  2.1.2
      ISO/IEC 10646                   2.1.6
      Label String                    2.1.10
      Language name codes             2.1.5
      Language Variant Table          2.1.11
      LDH Subset                      2.1.1
      Preferred Code Point            2.1.13
      Preferred Variant               2.1.13
      Preferred Variant Label         2.1.15
      Registration                    2.1.4
      Reserved                        2.1.18
      RFC3066                         2.1.5
      Table                           2.1.11
      UCS                             2.1.6
      Unicode Character               2.1.7
      Unicode String                  2.1.8
      Valid Code Point                2.1.12
      Variant Table                   2.1.11
      Zone Variant                    2.1.17

8. Acknowledgments

 The authors gratefully acknowledge the contributions of:
  1. V. CHEN, N. HSU, H. HOTTA, S. TASHIRO, Y. YONEYA, and other Joint

Engineering Team members at the JET meeting in Bangkok, Thailand.

  1. Yves Arrouye, an observer at the JET meeting in Bangkok, for his

contribution on the IDL Package.

  1. Those who commented on, and made suggestions about, earlier

versions, including Harald ALVESTRAND, Erin CHEN, Patrik

    FALTSTROM, Paul HOFFMAN, Soobok LEE, LEE Xiaodong, MAO Wei, Erik
    NORDMARK, and L.M. TSENG.

Konishi, et al. Informational [Page 28] RFC 3743 JET Guidelines for IDN April 2004

9. References

9.1. Normative References

 [ABNF]          Crocker, D. and P. Overell, Eds., "Augmented BNF for
                 Syntax Specifications: ABNF", RFC 2234, November
                 1997.
 [STD13]         Mockapetris, P., "Domain names concepts and
                 facilities" STD 13, RFC 1034, November 1987.
                 Mockapetris, P.,  "Domain names implementation and
                 specification", STD 13, RFC 1035, November 1987.
 [RFC3066]       Alvestrand, H., "Tags for the Identification of
                 Languages," BCP 47, RFC 3066, January 2001.
 [IDNA]          Faltstrom, P., Hoffman, P. and A. M. Costello,
                 "Internationalizing Domain Names in Applications
                 (IDNA)", RFC 3490, March 2003.
 [PUNYCODE]      Costello, A.M., "Punycode: A Bootstring encoding of
                 Unicode for Internationalized Domain Names in
                 Applications (IDNA)", RFC 3492, March 2003.
 [STRINGPREP]    Hoffman, P. and M. Blanchet, "Preparation of
                 Internationalized Strings ("stringprep")", RFC 3454,
                 December 2002.
 [NAMEPREP]      Hoffman, P. and M. Blanchet, "Nameprep: A Stringprep
                 Profile for Internationalized Domain Names (IDN)",
                 RFC 3491, March 2003.
 [IS10646]       A product of ISO/IEC JTC1/SC2/WG2, Work Item
                 JTC1.02.18 (ISO/IEC 10646).  It is a multipart
                 standard: Part 1, published as ISO/IEC 10646-
                 1:2000(E), covers the Architecture and Basic
                 Multilingual Plane, and Part 2, published as ISO/IEC
                 10646-2:2001(E), covers the supplementary
                 (additional) planes.
 [UNIHAN]        Unicode Han Database, Unicode Consortium
                 ftp://ftp.unicode.org/Public/UNIDATA/Unihan.txt.
 [UNICODE]       The Unicode Consortium, "The Unicode Standard Version
                 3.0," ISBN 0-201-61633-5.  Unicode Standard Annex #28
                 (http://www.unicode.org/unicode/reports/tr28/)
                 defines Version 3.2 of the Unicode Standard, which is
                 definitive for IDNA and this document.

Konishi, et al. Informational [Page 29] RFC 3743 JET Guidelines for IDN April 2004

 [ISO7098]       ISO 7098;1991 Information and documentation
                 Romanization of Chinese, ISO/TC46/SC2.

9.2. Informative References

 [IANA-LVTABLES] Internet Assigned Numbers Authority (IANA), IDN
                 Character Registry.
                 http://www.iana.org/assignments/idn/
 [IDN-WG]        IETF Internationalized Domain Names Working Group,
                 now concluded,idn@ops.ietf.org, James Seng, Marc
                 Blanchet, co-chairs, http://www.i-d-n.net/.
 [UDRP]          ICANN, "Uniform Domain Name Dispute Resolution
                 Policy", October 1999,
                 http://www.icann.org/udrp/udrp-policy-24oct99.htm
 [ISO639]     "ISO 639:1988 (E/F) Code for the representation of names
                 of languages", International Organization for
                 Standardization, 1st edition, 1988-04-01.

10. Contributors

 The formal responsibility for this document and the ideas it contains
 lie with K. Koniski, K. Huang, H. Qian, and Y. Ko.  These authors are
 listed on the first page as authors of record, and they are the
 appropriate the long-term contacts for questions and comments on this
 RFC.  On the other hand, J. Seng, J. Klensin, and W. Rickard served
 as editors of the document, transcribing and translating the ideas of
 the four authors and the teams they represented into the current
 written form.  They were the primary contacts during the editing
 process, but not in the long term.

Konishi, et al. Informational [Page 30] RFC 3743 JET Guidelines for IDN April 2004

10.1. Authors' Addresses

 Kazunori KONISHI
 JPNIC
 Kokusai-Kougyou-Kanda Bldg 6F
 2-3-4 Uchi-Kanda, Chiyoda-ku
 Tokyo 101-0047
 Japan
 Phone: +81 49-278-7313
 EMail: konishi@jp.apan.net
 Kenny HUANG
 TWNIC
 3F, 16, Kang Hwa Street, Taipei
 Taiwan
 Phone: 886-2-2658-6510
 EMail: huangk@alum.sinica.edu
 QIAN Hualin
 CNNIC
 No.6 Branch-box of No.349 Mailbox, Beijing 100080
 Peoples Republic of China
 EMail: Hlqian@cnnic.net.cn
 KO YangWoo
 PeaceNet
 Yangchun P.O. Box 81 Seoul 158-600
 Korea
 EMail: yw@mrko.pe.kr

Konishi, et al. Informational [Page 31] RFC 3743 JET Guidelines for IDN April 2004

10.2. Editors' Addresses

 James SENG
 180 Lompang Road
 #22-07 Singapore 670180
 Phone: +65 9638-7085
 EMail: jseng@pobox.org.sg
 John C KLENSIN
 1770 Massachusetts Avenue, No. 322
 Cambridge, MA 02140
 U.S.A.
 EMail: Klensin+ietf@jck.com
 Wendy RICKARD
 The Rickard Group
 16 Seminary Ave
 Hopewell, NJ  08525
 USA
 EMail: rickard@rickardgroup.com

Konishi, et al. Informational [Page 32] RFC 3743 JET Guidelines for IDN April 2004

11. Full Copyright Statement

 Copyright (C) The Internet Society (2004).  This document is subject
 to the rights, licenses and restrictions contained in BCP 78 and
 except as set forth therein, the authors retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at ietf-
 ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Konishi, et al. Informational [Page 33]

/data/webs/external/dokuwiki/data/pages/rfc/rfc3743.txt · Last modified: 2004/04/13 19:25 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki