3- While my 'proposal' includes modifications to the definition of quoted-
printable, the purpose of those modifications is really to remove from
it any traces of portable line ends. This is needed to make base64 and
quoted-printable idempotent, as stated everywhere.
There is at least one piece of text in MIME that might be worth taking
a closer look at to see if any changes are necessary (as far as the
quoted-printable newline issue is concerned):
The Content-Transfer-Encoding field is designed to specify
an invertible mapping between the "native" representation of
a type of data and a representation that can be readily
exchanged using 7 bit mail transport protocols, such as
those defined by RFC 821 (SMTP).
This may be a minor point, but I would say that it is quite possible
for someone to interpret the above text to mean that "loss-less"
conversions are possible using the transformations specified by the
content transfer encoding field. Specifically, the word "invertible"
may cause such people to interpret it in this way.
It should be noted that it is not possible to convert quoted-printable
back to the same sequence of bits if the sender's local newline
convention is not indicated somewhere. I.e. the information content of
the string "quoted-printable" is not sufficient to deduce that the
sender is using, say, UNIX. If loss-less conversion is deemed to be
required, a more informative indication would be something like
"quoted-printable/LF" (which means that LF is used for newlines on the
sender's system).
Note that I did not say that I feel that quoted-printable must be a
loss-less conversion. I will say, however, that I think that Base64
should be loss-less.
I suppose I would suggest that the above-quoted part of MIME be
altered slightly to indicate that a content transfer encoding may or
may not be "invertible". The section on quoted-printable already
states that Base64 may be preferrable in certain situations.
Alain, are there any other parts that would need further clarification
if we resolved things this way?
Regards,
Erik