Re: Use of LWSP in ABNF -- consensus call

On May 15, 2007, at 10:16 AM, John Leslie wrote:
>    I did some research, and found the following mentions of LWSP:
>
> rfc0733 obs-by rfc0822
> rfc0822 defs LWSP-char = SPACE / HTAB   obs-by rfc2822
> rfc0987 refs rfc0822
> rfc1138 refs rfc0822
> rfc1148 refs rfc0822
> rfc1327 refs rfc0822
> rfc1486 refs rfc0822
> rfc1505 refs rfc0822
> rfc1528 refs rfc0822
> rfc1848 defs <LWSP-char> ::= SPACE / HTAB
> rfc2017 refs rfc0822
> rfc2045 refs rfc0822
> rfc2046 refs rfc0822
> rfc2110 refs rfc0822
> rfc2156 refs rfc0822
> rfc2184 refs rfc0822
> rfc2231 refs rfc0822
> rfc2234 defs LWSP = *(WSP / CRLF WSP)   obs-by rfc4234
> rfc2243 refs rfc0822
> rfc2378 defs LWSP-char = SP | TAB
> rfc2530 refs rfc2234
> rfc2885 defs LWSP = *(WSP / COMMENT / EOL)
> rfc3015 defs LWSP = *(WSP / COMMENT / EOL)
> rfc3259 defs LWSP = *(WSP / CRLF WSP)
> rfc3501 refs rfc2234
> rfc3525 defs LWSP = *(WSP / COMMENT / EOL)
> rfc3875 defs LWSP = SP | HT | NL
> rfc4234 defs LWSP = *(WSP / CRLF WSP)
> rfc4646 refs rfc2434
>
>    Based on this, I recommend outright deprecation. The RFC4234
> definition is wildly different from the RFC822 usage (which is
> substanitally more often referenced): thus any use of it will tend
> to confuse. It's also a bit dubious, quite specifically allowing
> lines which appear to be blank, but aren't. :^(
>
>    The RFC4234 definition, in fact, is referenced by only 3 RFCs:
>
> RFC2530 Indicating Supported Media Features Using Extensions to DSN  
> and MDN
> RFC3501 INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1
> RFC4646 Tags for Identifying Languages
>
>    The use under RFC2530 is a bit vague ("with LWSP wrapping");  
> likewise
> under RFC3501 ("otherwise treat SP as being equivalent to LWSP"). The
> use under RFC4646 has caused known problems.
>
>    This would seem to justify deprecation, IMHO.

Agreed.

 From a standards standpoint, half a dozen definitions for an ABNF  
mnemonic is absurd.

Perhaps something like:

The LWSP mnemonic has been deprecated and should not be used in  
future drafts.  Explicit definitions based upon different mnemonics  
should be used instead.  If possible, syntax should guard against  
possible security concerns related to visual deceptions.

-Doug

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