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Re: Prohibition of EBCDIC in text/plain

1995-06-09 11:11:48
Keith Moore <moore(_at_)cs(_dot_)utk(_dot_)edu> writes:
Fortunately, as long as *all* incoming MIME messages go through this
translation, you can deal with the change.  If you're on an EBCDIC
machine, and if you see "text/plain; charset=US-ASCII", you know that
the message is really ASCII translated to EBCDIC (and so should your
user agent).

The wording I recently suggested adding to the "Canoncial Encoding
Model" is appropriate here.

What you have here is a MIME message where the text/plain part really
is in US-ASCII.  It's just that the entire MIME message has gone
through an encoding where each octet has been replaced by the
corresponding octet from the ASCII-->EBCDIC translation table.

To read the message, you have to first remove the local-form encoding
by running each octet through the EBCDIC-->ASCII translation table.
Then, you can interpret the MIME structure and extract the US-ASCII
text/plain part.  If you want, you can then convert the US-ASCII
text/plain part back into EBCDIC when saving it to a file.

This Canonical Encoding Model is *very important*, especially in the
face of such things as binary objects, MD5 hashes, and digital

If you try to define a format which is MIME, but where all occurences
of "US-ASCII" are replaced with "EBCDIC" gives you a format which is
*incompatible* with MIME.

_.John G. Myers         Internet: jgm+(_at_)CMU(_dot_)EDU
                        LoseNet:  ...!seismo!ihnp4!!give!up

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