Review of draft-philips-langtags-03: ABNF errors

[Harald Tveit Alvestrand]

--On 23. juni 2004 15:42 -0700 Mark Davis <mark.davis at jtcsv.com> wrote:

> We are using =/ as defined in the RFC
> (ftp://ftp.isi.edu/in-notes/rfc2234.txt)

No, you're not - the spec says that the "ruleset" token has to be on the 
front of EVERY production, not just the first one.

                        Harald

>
> .3  Incremental Alternatives                    Rule1 =/ Rule2
>
>    It is sometimes convenient to specify a list of alternatives in
>    fragments.  That is, an initial rule may match one or more
>    alternatives, with later rule definitions adding to the set of
>    alternatives.  This is particularly useful for otherwise- independent
>    specifications which derive from the same parent rule set, such as
>    often occurs with parameter lists.  ABNF permits this incremental
>    definition through the construct:
>
>         oldrule     =/ additional-alternatives
>
>    So that the rule set
>
>         ruleset     =  alt1 / alt2
>
>         ruleset     =/ alt3
>
>         ruleset     =/ alt4 / alt5
>
>    is the same as specifying
>
>         ruleset     =  alt1 / alt2 / alt3 / alt4 / alt5
>
> For spaces, we were using them for readability (not that ABNF is
> particularly readable anyway), but it appears that we shouldn't:
>
>         For Internet
>         specifications, there is some history of permitting linear white
>         space (space and horizontal tab) to be freelyPand
>         implicitlyPinterspersed around major constructs, such as
>         delimiting special characters or atomic strings.
>
>         NOTE:     This specification for ABNF does not
>                   provide for implicit specification of linear white
>                   space.
>
>    Any grammar which wishes to permit linear white space around
>    delimiters or string segments must specify it explicitly.  It is
>    often useful to provide for such white space in "core" rules that are
>    then used variously among higher-level rules.  The "core" rules might
>    be formed into a lexical analyzer or simply be part of the main
>    ruleset.
>
>
> Mark
> __________________________________
> http://www.macchiato.com
> ? ????????????????????? ?
>
> ----- Original Message -----
> From: "Harald Tveit Alvestrand" <harald at alvestrand.no>
> To: <ietf-languages at iana.org>
> Sent: Wed, 2004 Jun 23 13:08
> Subject: Review of draft-philips-langtags-03: ABNF errors
>
>
>> I have at last started to seriously review this document, with a view to
>> offering my opinion to the IESG for their perusal - I'll recuse on the
>> processing itself.
>>
>> But - the ABNF is NOT ready for prime time.
>>
>> The authors seem to believe that =/ is a continuation symbol (it is not),
>> and that there is a space between the number-quantifier and the rule it
>> quantifies (there isn't).
>>
>> Also, "x" strings are case-insensitive, so they can't be used in ranges -
>> hex codes have to be used.
>>
>> And underscores aren't allowed in rule names.
>>
>> Here's a grammar for the stuff that at least parses correctly:
>> ------------------------------------------------------------
>> langtag   = lang *("-" extlang) ["-" script] ["-" region]
>> *("-" variant) *("-" extension) *("-" private-use)
>>       / private-use       ; private use tag
>>       / grandfathered     ; grandfathered registrations
>>
>> lang            = 2*3ALPHA                ; shortest ISO 639 code
>> / registered-lang
>> extlang         = 3ALPHA                  ; reserved for future use
>> script          = 4ALPHA                  ; ISO 15924 code
>> region          = 2ALPHA                  ; ISO 3166 code
>> / 3DIGIT                 ; UN country number
>> variant         =  5*15alphanum           ; registered or private use
>> variants
>> extension       = singleton 1*("-" (2*31alphanum)) ; extension subtag(s)
>> private-use     = "x" 1*("-" (1*31alphanum))       ; private use
>> subtag(s) singleton       = ALPHA      ; single letters - x has spec
>> meaning registered-lang = 4*15ALPHA               ; registered language
>> subtag grandfathered   = ALPHA *(alphanum / "-") ; grandfathered
>> registration alphanum        = (ALPHA / DIGIT)          ; letters and
>> numbers
>>
>>
>>
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>>
>
>