Tags for the Identification of Languages
RFC 3066
Document | Type |
RFC - Best Current Practice
(January 2001; Errata)
Obsoletes RFC 1766
Was draft-alvestrand-lang-tag-v2 (individual)
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Author | Harald Alvestrand | ||
Last updated | 2020-01-21 | ||
Stream | Legacy | ||
Formats | plain text html pdf htmlized with errata bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 3066 (Best Current Practice) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group H. Alvestrand Request for Comments: 3066 Cisco Systems BCP: 47 January 2001 Obsoletes: 1766 Category: Best Current Practice Tags for the Identification of Languages Status of this Memo This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. Abstract This document describes a language tag for use in cases where it is desired to indicate the language used in an information object, how to register values for use in this language tag, and a construct for matching such language tags. 1. Introduction Human beings on our planet have, past and present, used a number of languages. There are many reasons why one would want to identify the language used when presenting information. In some contexts, it is possible to have information available in more than one language, or it might be possible to provide tools (such as dictionaries) to assist in the understanding of a language. Also, many types of information processing require knowledge of the language in which information is expressed in order for that process to be performed on the information; for example spell-checking, computer-synthesized speech, Braille, or high-quality print renderings. One means of indicating the language used is by labeling the information content with an identifier for the language that is used in this information content. Alvestrand Best Current Practice [Page 1] RFC 3066 Tags for Identification of Languages January 2001 This document specifies an identifier mechanism, a registration function for values to be used with that identifier mechanism, and a construct for matching against those values. The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119]. 2. The Language tag 2.1 Language tag syntax The language tag is composed of one or more parts: A primary language subtag and a (possibly empty) series of subsequent subtags. The syntax of this tag in ABNF [RFC 2234] is: Language-Tag = Primary-subtag *( "-" Subtag ) Primary-subtag = 1*8ALPHA Subtag = 1*8(ALPHA / DIGIT) The productions ALPHA and DIGIT are imported from RFC 2234; they denote respectively the characters A to Z in upper or lower case and the digits from 0 to 9. The character "-" is HYPHEN-MINUS (ABNF: %x2D). All tags are to be treated as case insensitive; there exist conventions for capitalization of some of them, but these should not be taken to carry meaning. For instance, [ISO 3166] recommends that country codes are capitalized (MN Mongolia), while [ISO 639] recommends that language codes are written in lower case (mn Mongolian). 2.2 Language tag sources The namespace of language tags is administered by the Internet Assigned Numbers Authority (IANA) [RFC 2860] according to the rules in section 3 of this document. The following rules apply to the primary subtag: - All 2-letter subtags are interpreted according to assignments found in ISO standard 639, "Code for the representation of names of languages" [ISO 639], or assignments subsequently made by the ISO 639 part 1 maintenance agency or governing standardization bodies. (Note: A revision is underway, and is expected to be released as Alvestrand Best Current Practice [Page 2] RFC 3066 Tags for Identification of Languages January 2001 ISO 639-1:2000) - All 3-letter subtags are interpreted according to assignments found in ISO 639 part 2, "Codes for the representation of names of languages -- Part 2: Alpha-3 code [ISO 639-2]", or assignments subsequently made by the ISO 639 part 2 maintenance agency or governing standardization bodies. - The value "i" is reserved for IANA-defined registrations - The value "x" is reserved for private use. Subtags of "x" shall not be registered by the IANA. - Other values shall not be assigned except by revision of this standard. The reason for reserving all other tags is to be open towards new revisions of ISO 639; the use of "i" and "x" is the minimum we can do here to be able to extend the mechanism to meet our immediate requirements. The following rules apply to the second subtag: - All 2-letter subtags are interpreted as ISO 3166 alpha-2 country codes from [ISO 3166], or subsequently assigned by the ISO 3166 maintenance agency or governing standardization bodies, denotingShow full document text