Variant subtags for non-ISO-15924 scripts (was Re: Variant subtag request: iso91995)

Doug Ewell doug at
Thu Sep 16 16:09:08 CEST 2010

Philip Newton <philip dot newton at gmail dot com> wrote:

> Are (a) and (b) really options? I thought those were only for
> varieties of a language.

All subtags beyond language and extlang are "for varieties of a
language" in some sense.  Region subtags denote the way a language is
used in one region as opposed to another region; script subtags denote
the writing system in which a language is written.

Variants are typically used for other types of variation, since the
assumption of BCP 47 is that the standards bodies for ISO 3166 and 15924
and UN M.49 will encode, *more or less*, those entities that are useful
for language tagging.  The fit isn't always perfect, because it's not
the responsibility of the standards bodies to make their standards match
BCP 47, and so we have variants for things like Scottish English and

It's certainly not within the scope of the standards bodies to provide a
code element for every invented language or script that someone dreams
up in their spare time.  But they are still languages and scripts, and
if sufficient demand exists to interchange content in these languages or
scripts (which I do not necessarily claim is the case for Ewellic), then
a registered variant might be appropriate.

Private-use subtags in "x-" are strictly user-defined.  They can mean
pretty much anything you want them to mean.  If you think
"FileListBuildProgressDlg" is a type of English usage specific to
software developers, or for that matter a different language entirely,
you are at liberty to tag it as "en-x-softdev" or "x-softdev".

> So the take-away is: variant subtags and private-use subtags can also
> represent scripts?

According to Section 2.2.5 of RFC 5646:

"Variant subtags are used to indicate additional, well-recognized
variations that define a language or its dialects that are not covered
by other available subtags."

and according to Section 2.2.7:

"Private use subtags are used to indicate distinctions in language that
are important in a given context by private agreement."

I interpret "variations" and "distinctions" to include those that might
have been covered in another type of subtag (region or script), if that
subtag value were available.

There are advantages and disadvantages to using a private-use script
subtag in the Qaaa-Qabx range, versus using a variant or private-use
"x-" subtag where the name "ewellic" could be spelled out.  As described
in Section 4.6, the syntax of the subtag 'Qabe' clearly denotes a
script, information that the other options do not provide.  The extent
to which one prefers "en-Qabe" over "en-(x-)ewellic" probably depends on
the extent to which one believes that language tags are meant for
processes rather than human readers.

Doug Ewell | Thornton, Colorado, USA |
RFC 5645, 4645, UTN #14 | ietf-languages @ is dot gd slash 2kf0s ­

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