From: Charles Lindsey (chl@clerew.man.ac.uk)
Date: Mon May 19 2003 - 05:11:26 CDT
In <3EC5099F.8040800@Sonietta.blilly.com> Bruce Lilly <blilly@erols.com> writes:
>Charles Lindsey wrote:
>> In <3EBFA5C8.9080704@Sonietta.blilly.com> Bruce Lilly <blilly@erols.com> writes:
>> No, there is always the choice between describing it syntactically and
>> describing it by verbiage.
>There will be syntax at least in the form of ABNF. Any verbiage must
>be consistent with that ABNF and vice versa.
On the contrary. The verbiage must never attempt to permit that which is
forbidden by the ABNF, but it is common practice for the verbiage to
provide additional restrictions so as to exclude what the ABNF would
otherwise have allowed. Pete has provided an example from RFC 2822.
The reason is that some such restrictions would require so many pages of
additional ABNF as to render the whole thing unreadble.
>Example of contradiction:
> The From-header contains the email address(es), possibly including
> the full name(s), of the article's poster(s). The content syntax
> makes use of syntax defined in [RFC 2822].
> header =/ From-header
> From-header = "From" ":" SP From-content
> From-content = mailbox-list
>Assuming that "mailbox-list" refers to the 2822 production (it's not in
>the list of imported productions in sect. 2.4), that most certainly does
>not incorporate the must-have-non-whitespace-content-on-initial-field-line
>rule since mailbox-list provides for line folding at its start.
If you think that particular requirement could have been expressed in
ABNF, then please show us your syntax for doing so.
-- Charles H. Lindsey ---------At Home, doing my own thing------------------------ Tel: +44 161 436 6131 Fax: +44 161 436 6133 Web: http://www.cs.man.ac.uk/~chl Email: chl@clerew.man.ac.uk Snail: 5 Clerewood Ave, CHEADLE, SK8 3JU, U.K. PGP: 2C15F1A9 Fingerprint: 73 6D C2 51 93 A0 01 E7 65 E8 64 7E 14 A4 AB A5