Network Working Group                                      H. Alvestrand
Request for Comments: 1766                                       UNINETT
Category: Standards Track                                     March 1995


                Tags for the Identification of Languages

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This document describes a language tag for use in cases where it is
   desired to indicate the language used in an information object.

   It also defines a Content-language: header, for use in the case where
   one desires to indicate the language of something that has RFC-822-
   like headers, like MIME body parts or Web documents, and a new
   parameter to the Multipart/Alternative type, to aid in the usage of
   the Content-Language: header.

1.  Introduction

   There are a number of languages spoken by human beings in this world.

   A great number of these people would prefer to have information
   presented in a language that they understand.

   In some contexts, it is possible to have information in more than one
   language, or it might be possible to provide tools for assisting in
   the understanding of a language (like dictionaries).

   A prerequisite for any such function is a means of labelling the
   information content with an identifier for the language in which is
   is written.

   In the tradition of solving only problems that we think we
   understand, this document specifies an identifier mechanism, and one
   possible use for it.








 
RFC 1766                      Language Tag                    March 1995


2.  The Language tag

   The language tag is composed of 1 or more parts: A primary language
   tag and a (possibly empty) series of subtags.

   The syntax of this tag in RFC-822 EBNF is:

    Language-Tag = Primary-tag *( "-" Subtag )
    Primary-tag = 1*8ALPHA
    Subtag = 1*8ALPHA

   Whitespace is not allowed within the tag.

   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.

   The namespace of language tags is administered by the IANA according
   to the rules in section 5 of this document.

   The following registrations are predefined:

   In the primary language tag:

    -    All 2-letter tags are interpreted according to ISO standard
         639, "Code for the representation of names of languages" [ISO
         639].

    -    The value "i" is reserved for IANA-defined registrations

    -    The value "x" is reserved for private use. Subtags of "x"
         will not be registered by the IANA.

    -    Other values cannot be assigned except by updating 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