| Note | The values for this attribute are language
‘tags’ as defined in BCP 47. Currently
BCP 47 comprises RFC 4646 and RFC 4647; over time, other IETF
documents may succeed these as the best current practice. A ‘language tag’, per BCP 47, is assembled
from a sequence of components or subtags separated by
the hyphen character ( -, U+002D). The tag
is made of the following subtags, in the following order. Every
subtag except the first is optional. If present, each occurs only
once, except the fourth and fifth components (variant and
extension), which are repeatable.
- language
- The IANA-registered code for the language. This is almost
always the same as the ISO 639 2-letter language code if there
is one. The list of available registered language subtags can be
found at http://www.iana.org/assignments/language-subtag-registry.
It is recommended that this code be written in lower
case.
- script
- The ISO 15924 code for the script. These codes consist of
4 letters, and it is recommended they be written with an initial
capital, the other three letters in lower case. The canonical
list of codes is maintained by the Unicode Consortium, and is
available at http://unicode.org/iso15924/iso15924-codes.html. The
IETF recommends this code be omitted unless it is necessary to
make a distinction you need.
- region
- Either an ISO 3166 country code or a UN M.49 region code
that is registered with IANA (not all such codes are registered,
e.g. UN codes for economic groupings or codes for countries for
which there is already an ISO 3166 2-letter code are not
registered). The former consist of 2 letters, and it is
recommended they be written in upper case. The list of codes can
be found at http://www.iso.org/iso/en/prods-services/iso3166ma/02iso-3166-code-lists/index.html.
The latter consist of 3 digits; the list of codes can be found
at http://unstats.un.org/unsd/methods/m49/m49.htm.
- variant
- An IANA-registered variation. These codes ‘are used to indicate additional, well-recognized
variations that define a language or its dialects that are not
covered by other available subtags’.
- extension
- An extension has the format of a single letter followed by
a hyphen followed by additional subtags. These exist to allow
for future extension to BCP 47, but as of this writing no such
extensions are in use.
- private use
- An extension that uses the initial subtag of the single
letter x (i.e., starts with
x-) has no meaning except as negotiated among the
parties involved. These should be used with great care, since
they interfere with the interoperability that use of RFC 4646 is
intended to promote. In order for a document that makes use of
these subtags to be TEI conformant, a corresponding
language element must be present in the TEI
header.
There are two exceptions to the above format. First, there are
language tags in the IANA
registry that do not match the above syntax, but are present
because they have been ‘grandfathered’ from
previous specifications. Second, an entire language tag can consist of only a private use
subtag. These tags start with x-, and do not need to
follow any further rules established by the IETF and endorsed by
these Guidelines. Like all language tags that make use of private use
subtags, the language in question must be documented in a
corresponding language element in the TEI header. Examples include
- sn
- Shona
- zh-TW
- Taiwanese
- zh-Hant-HK
- Chinese written in traditional script as used in Hong Kong
- en-SL
- English as spoken in Sierra Leone
- pl
- Polish
- es-MX
- Spanish as spoken in Mexico
- es-419
- Spanish as spoken in Latin America
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