At 14:44 15-08-2007, Charles Lindsey wrote:
>2.1.1. Line Length Limits
>
> There are two limits that this specification places on the number of
> characters in a line. Each line of characters MUST be no more than
> 998 characters, and SHOULD be no more than 78 characters, excluding
> the CRLF.
Can we de-emphasise that SHOULD, and make it clear that this is a matter
of good practice (in the sense of BCP) rather than a normative feature?
Perhaps s/SHOULD/should/? Too many agents have used this as an excuse to
rewrite lines en route (maybe there should be a SHOULD NOT for that).
I read that as more than a BCP. Quoting a message from the 2822 era:
"The 78 character recommendation is due to limitations in many
implementations which display these messages which may truncate display
of more than 78 characters per line. Of course, even though these
limitations are put on messages, interpreters of messages would do well
to handle an arbitrarily large number of characters in a line, including
for display, for robustness' sake."
Where did that '78' come from? I am aware of lots of systems that do
horrid things such as you mention if there are 80 characters in a line,
but I am aware of none where problems arise with exactly 79. In other fora
where I have seen this discussed, the consensus was that exceeding '79'
was the signal for troubles to start.
There are 80 characters per line on a text display. There may be a
one character border on the left and right hand side. That leaves
you with 78 characters. Some (old) displays do not wrap a long
line. Although it may sound obsolete in this day and age, some
messages may be sent directly to a printer which may have the same line limit.
>3.3. Date and Time Specification
> A date-time specification MUST be semantically valid. That is, the
> day-of-week (if included) MUST be the day implied by the date, the
> numeric day-of-month MUST be between 1 and the number of days allowed
> for the specified month (in the specified year), the time-of-day MUST
> be in the range 00:00:00 through 23:59:60 (the number of seconds
> allowing for a leap second; see [RFC1305]), and the zone MUST be
> within the range -9959 through +9959.
why not "within the range -2359 through +2359"?
Because the difference can be more than 2359. If I recall correctly,
it was something to do with crossing the date line.
Regards,
-sm