en-boont-scouse?

[Doug Ewell]

Variant subtags under RFC 3066bis are defined as having a "recommended
prefix," such that they are considered appropriate for use with language
tags that match that prefix and not appropriate (though still valid)
with those that do not.

For example, the variant subtag 'scouse' has a recommended prefix of
'en', so that "en-scouse" is sensible and valid, while "ar-scouse" is
silly but still valid.

Variant subtags can have more than one recommended prefix (hereafter
"RP"), although no such subtags are currently proposed.  Also, a
language tag can have more than one variant subtag.  For example, a
while back, Han Steenwijk proposed subtags for sub-dialects of the
Resian dialect of Slovenian.  In the RFC 3066bis environment, these
would be variant subtags with an RP of 'sl-rozaj' instead of merely
'sl'.  This way, for example, a user could write "sl-rozaj-ravan" to
indicate the Ravanca sub-dialect.  Switching the subtags around, as
'sl-ravan-rozaj', or would still be technically valid but would no
longer follow the intent of the RP mechanism, because the qualifying
prefix for 'ravan' would be 'sl' and not 'sl-rozaj'.

Variant subtags can be registered to represent concepts other than
dialects and sub-dialects.  The subtags '1901' and '1996' are intended
to be used with the prefix 'de' to indicate the spelling conventions
that were first promulgated in those years (more or less).  If there
were *also* a variant subtag to indicate a specific sub-dialect of
German, say 'xyzzy', it would be perfectly reasonable to write any of
the following:

de-1901
de-1996
de-xyzzy

and also:

de-1901-xyzzy
de-1996-xyzzy
de-xyzzy-1901
de-xyzzy-1996

Of the latter four, the first and third would somehow have to be
considered equivalent, as would the second and fourth.

The point is that 'xyzzy' would only have to have an RP of 'de', and not
'de-1901', in order to be used reasonably with 'de-1901'.  It would
clearly be appropriate to use these variant subtags together, as well as
separately, because they do not represent mutually exclusive concepts.

I am wondering about the "recommended-ness" of a language tag that
contains two or more variant subtags that have the same RP, but which
are *not* intended to be used together, because they do represent
mutually exclusive concepts.  Currently, the following language tags
would be not only valid, but would also adhere to the letter of the law
concerning RPs; however, they are obviously preposterous:

en-boont-scouse
de-1901-1996
sl-nedis-rozaj
zh-guoyu-hakka-xiang (or pick any two)

Switching the order of the variant subtags in the tags above would be
equally preposterous.

What is the policy, or what should it be, concerning such tags?  It
would not be desirable to restrict the RP concept so that any variant
subtags in the "base" tag must be indicated in the RP, because that
would remove legitimacy from the "de-1901-xyzzy" example above.  Yet
"en-boont-scouse" (which passes the RP test) is clearly as silly a tag
as "ar-scouse" (which fails it), and for the same reason.

Please note that I am asking this for my own clarification, NOT to stall
or derail the approval process for RFC 3066bis in any way.  My validator
says that "ar-scouse" violates the RP test, but "en-boont-scouse" does
not, and I want to know if that is correct.

-Doug Ewell
 Fullerton, California
 http://users.adelphia.net/~dewell/