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Guidelines for Developing Reference Label Generation Rules (LGRs) for the Second Level Version 2

Open Date: 30 March 2020 Close Date: 12 May 2020
Originating Organization: Global Domains Division
Categories/Tags: Second-Level Domains
Brief Overview:

ICANN org had published reference Label Generation Rules (LGRs) for multiple languages to facilitate the security and stability of Internationalized Domain Name (IDN) operations of generic Top Level Domain (gTLD) registries and improve transparency and consistency of testing IDN tables. The existing guidelines used for these reference IDN tables focus on developing language-based reference LGRs. Since then, the detailed analyses of multiple scripts have been completed for the Root Zone Label Generation Rules (RZ-LGR) by the relevant communities. These analyses can now be used for creating reference second-level LGRs for these scripts. Therefore, the Guidelines for Developing Reference LGRs for the Second Level are being updated to also include details of how to design script-based reference LGRs in addition to language-based reference LGRs. These guidelines are published for community feedback on the proposed methodology. Based on these guidelines, which will be finalized after incorporating the input from the community, ICANN org will continue to develop the IDN tables for additional languages and scripts and post these for public comment.


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Domain Name System
Internationalized Domain Name ,IDN,"IDNs are domain names that include characters used in the local representation of languages that are not written with the twenty-six letters of the basic Latin alphabet ""a-z"". An IDN can contain Latin letters with diacritical marks, as required by many European languages, or may consist of characters from non-Latin scripts such as Arabic or Chinese. Many languages also use other types of digits than the European ""0-9"". The basic Latin alphabet together with the European-Arabic digits are, for the purpose of domain names, termed ""ASCII characters"" (ASCII = American Standard Code for Information Interchange). These are also included in the broader range of ""Unicode characters"" that provides the basis for IDNs. The ""hostname rule"" requires that all domain names of the type under consideration here are stored in the DNS using only the ASCII characters listed above, with the one further addition of the hyphen ""-"". The Unicode form of an IDN therefore requires special encoding before it is entered into the DNS. The following terminology is used when distinguishing between these forms: A domain name consists of a series of ""labels"" (separated by ""dots""). The ASCII form of an IDN label is termed an ""A-label"". All operations defined in the DNS protocol use A-labels exclusively. The Unicode form, which a user expects to be displayed, is termed a ""U-label"". The difference may be illustrated with the Hindi word for ""test"" — परीका — appearing here as a U-label would (in the Devanagari script). A special form of ""ASCII compatible encoding"" (abbreviated ACE) is applied to this to produce the corresponding A-label: xn--11b5bs1di. A domain name that only includes ASCII letters, digits, and hyphens is termed an ""LDH label"". Although the definitions of A-labels and LDH-labels overlap, a name consisting exclusively of LDH labels, such as"""" is not an IDN."