Request to register private-use variant subtags

Gordon P. Hemsley gphemsley at
Sun Apr 8 00:13:09 CEST 2012

On Sat, Apr 7, 2012 at 5:10 PM, Doug Ewell <doug at> wrote:
> Gordon P. Hemsley wrote:
>>> Though I note that there would be a difference between such putative
>>> private use variant subtags and the -x- mechanism: everything
>>> (including other singletons) after -x- is private use, that would not
>>> be the case for private use variant subtags.
>> This is an important point that I hadn't even thought of. Private use
>> subtags allow for localized private use—that is, for only a particular
>> type of subtag. I think there is a difference between a private-use
>> variant (= a variant that just so happens to not be registered) and a
>> private-use -x- extension (= could be anything under the sun, like the
>> '-x-ignore-this-subtag' that I've also used in my tests).
> A subtag of any registered type (language, extlang, script, region, variant)
> that "just so happens to not be registered" is invalid for use in any tag or
> language-range.

Sorry, that was a poor choice of words. What I meant was, you know
that it's a variant, even if you don't know what it means, and it
doesn't affect any other part of the language tag. This differs from
the -x- extension, which could be used for anything, and which makes
everything after it also be private use.

> Testing is another matter; you are strongly encouraged to
> test your application or engine against non-registered subtags, to ensure
> that they are properly detected as invalid.

That is all well and good, but my primary goal in this particular case
is not to check validity.

> Later:
>>> I don't see why we should encode subtags for testing purposes. For
>>> personal use OR for corporate use.
>> Just so I'm clear: If it were up to you, there wouldn't be private-use
>> subtags for language, region, or script, either?
> 1. Michael didn't say that.

I know he didn't say that directly. But testing, IMO, is a perfectly
valid "private use". So why should there be private-use subtags for
language, region, and script, but not for variant? The impression I
keep getting is that the existing private use subtags are in the
Registry simply because they're in the ISO standards, not because
anyone thought they might actually be used for something. And since
the variant subtags are not related to any ISO standard, there are no
private-use variant subtags that are forced to be registered.

> 2. As I did say last week, private-use subtags for language, region, and
> script aren't for testing purposes. They are based on code elements in ISO
> 639, 3166, and 15924 respectively, which were primarily intended for people
> using those standards directly. They can also be used in BCP 47, but with
> the assumption that there is a private agreement that governs their use, not
> to mean "nothing" or "invalid."
> More information on the intended use of subtags like 'qaa' is available in
> RFC 5646, sections 2.2.1 (point 3), 2.2.3 (point 3), 2.2.4 (point 3), and
> 4.6, as well as the following passage from Section 2.2.9:
> "Subtags designated for private use as well as private use sequences
> introduced by the 'x' subtag are available for cases in which no assigned
> subtags are available and registration is not a suitable option.  For
> example, one might use a tag such as "no-QQ", where 'QQ' is one of a range
> of private use ISO 3166-1 codes to indicate an otherwise undefined region."

Unicode seems to have asserted by "private agreement" that 'ZZ'
represents "Unknown or Invalid Territory". [1][2] I see no reason why
I can't, for example, assert by "private agreement" that 'QZ'
represents "Testing Region".

I have read all those sections, and I see nothing that dictates what
kind of parameters my "private use" must abide by. As far as I can
see, I am welcome to privately agree to any meaning for any private
use subtag. In addition, the passage you quote goes on to say:

"Users MUST NOT assign language tags that
   use subtags that do not appear in the registry other than in private
   use sequences (such as the subtag 'personal' in the tag "en-x-
   personal").  Besides not being valid, the user also risks collision
   with a future possible assignment or registrations."

It is precisely this that I am trying to abide by when I request a
private use variant subtag.

I want to emphasize again the fact that there does not seem to be any
restriction on the Registry from registering private use variant

Section 2.2.5, point 2:

"Variant subtags, as a collection, are not associated with any
       particular external standard.  The meaning of variant subtags in
       the registry is defined in the course of the registration process
       defined in Section 3.5.  Note that any particular variant subtag
       might be associated with some external standard.  However,
       association with a standard is not required for registration."


Gordon P. Hemsley
me at

More information about the Ietf-languages mailing list