Re: Use of LWSP in ABNF -- consensus call

Paul Overell <paul.overell@thus.net> wrote:
> In message <464926FC.30109@att.com>, Tony Hansen <tony@att.com> writes
>> Lisa Dusseault wrote:
>> 
>>> I share your concerns about removing rules that are already in use --
>>> that would generally be a bad thing.  However I'm interested in the
>>> consensus around whether a warning or a deprecation statement would be
>>> a good thing.
>>
>> LWSP has a valid meaning and use, and its being misapplied somewhere
>> doesn't make that meaning and usage invalid.
> 
> Agreed - well put.
> 
>> I could see a note being
>> added. However, anything more than that is totally inappropriate.
> 
> I would vote against even adding a note.  It seems disproportionate to 
> change a 10 year specification at this late stage on the basis of a 
> single case of a misapplied, but valid, rule in another specification.

   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.

   YMMV, of course...

--
John Leslie <john@jlc.net>

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