John Cowan wrote:
>>>> 1*3ALPHA 1*2("-" (2*8alphanum))
> I still don't understand the purpose of the second
> alternative.
Right, now I also see it. An enumeration is useful if
it could be mistaken as well-formed "regular" tag. For
a parser it's important to match some "irregular" tags
_before_ it starts to match the "regular" tags.
From that POV x-anything and i-anything are harmless,
they're never ambiguous. And sgn-BE-nl or en-GB-oed
are also not critical, they never match "regular" tags,
because they're not well-formed.
At some point (not necesarily a.s.a.p.) they have to
match, after all they're valid. Therefore these tags
could be enumerated as part of <irregular>.
The critical tags are well-formed grandfathered tags
like zh-xiang, because there is no registered variant
xiang (at the moment).
You're trying to clean it up for boont and scouse, if
that's accepted we end up with nine critical tags:
art-lobjan, cel-gaulish, no-nyn, no-bok, zh-guoyu,
zh-hakka, zh-min, zh-min-nan, zh-xiang.
We're free to do whatever we like with the potential
variants in those tags (declare them to be reserved,
or deprecate them).
We cannot preempt bok, min, nan and nyn, and they'll
be used soon (probably):
- bok is a future language subtag
- min is a future language subtag
- nan is a future extlang (and even related, good)
- nyn is a future language subtag
So from the 9 (or 11) critical tags we get a subset
of 4 tags "no-extlang-or-not-what-you-might-expect".
That results in about four subsets for an improved
grandfathered ABNF:
13 i-anything, detailed ABNF enumeration unnecessary
4 extlang bogeys: no-bok, no-nyn, zh-min, zh-min-nan
5 variant bogeys: art-lobjan, cel-gaulish, etc.
2 variant bogeys which might go away before "date C"
4 less critical: en-GB-oed, and the three sgn-XX-yy
If the ABNF is improved we should consider to support
left-to-right depth-first matching, or in other words
mention <grandfathered> _before_ <langtag>.
Frank
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