ietf-822
[Top] [All Lists]

ISO-CHARSET-TYPE -- some comments

1991-04-22 23:02:50
ISO-CHARSET-TYPE -- Indicates the document contains text in an ISO
standard character set by ints International Registration number.  Each
ISO character set defines a new standard mail content type, given by the
string "ISO-IR-" followed by the numeric value of the character set. 
Thus, for example, a content-type of "ISO-IR-6" specifies a character
set that is extremely similar, and perhaps identical, to MAILASCII. 

ISO-IR-6 only contains the 94 characters between space and delete
*exclusive*, and is therefore not even close to MAILASCII, which
contains all the control characters and space as well.


However, it should be noted that even when the Content-type is an
ISO-IR- character set type, certain control characters will always be
construed according to the guidelines of RFC 821 and RFC 822.  In
particular, character positions 13, 10, and 32 will always be
interpreted at times as CR, LF, and SPACE, respectively.

"always ... at times" ??? :-)


Wouldn't it be better to specify that only the single-byte
94-character sets are allowed in ISO-IR-n?

I don't think the multibyte sets should be allowed since they would be
encoded together with ASCII within the framework of ISO 2022, which I
think needs its own Content-Type name.

Also, the single-byte 96-character sets should not be allowed since
they have the 8th bit up and are usually used together with ASCII to
form e.g. Latin-1. I think Latin-1 should be given its own
Content-Type, and it can be encoded in Quoted-Printable, or something
similar (e.g. quoted-readable \"u).

Finally, we shouldn't allow control character sets, for the reasons
that you give above.

Would it be helpful to include a list of currently allowed character
sets in an Appendix or something?

Another approach would be to acknowledge that what we are really
trying to support are the national ISO 646 variants. So you might give
the Content-Type a name like this:

        ISO-646-<registration-number>

E.g.

        ISO-646-4       (for the United Kingdom)

Comments? Keld?


Regards,
Erik


<Prev in Thread] Current Thread [Next in Thread>