Date: Tue, 8 Jun 93 20:44:26 +0200
From: Olle Jarnefors <ojarnef(_at_)admin(_dot_)kth(_dot_)se>
Subject: IANA policy regarding character sets
IANA registers one type of objects, namely character sets, in
two different name spaces. There is a group of character sets
registered under the heading "MIME TYPES", subheading "Character
Sets", on pages 77 and 78 in RFC 1340, and another group of
character sets under its own heading "CHARACTER SETS" on pages
The next edition of Assigned Numbers will clarify this. Just before the
list of character sets now on page 77 the following text will appear:
"All of the character sets listed in the following section on Character
Sets (which starts on page 79 in RFC 1340) are registered for use with
MIME as MIME Character Sets. The correspondance between the few character
sets listed in the MIME specification  and the list in the next
The same character set usually has different names in the two
groups. For example US-ASCII in the first group is the same as
ANSI_X3.4-1968 in the second and ISO-8859-1 in the first is the
same as ISO_8859-1:1987 in the second.
As noted above the small list on page 77 will be a correspondance table
to find the name used in RFC-1341 in the main list on page 79.
The current handling of character set registration is bound to
1) What is the reason for the double registration of character
That RFC-1341 defined some names in its own way. Just a bit later
a significant list of character set was documented in RFC-1345.
2) What is the purpose of the second group of character set
The character set names should be defined in general, not just the MIME
context. The second set of names should become the official set. The
second set of names shold be used to identify character sets in all RFCs,
not just MIME documents.
3) Will this purpose be clearly stated in the successor to RFC
1340? (That may counteract the widely spread misconception
that the names in the second group can be used in MIME.)
The names in the second set CAN be used in MIME. This will be clearly
indicated in the next edition of Assigned Numbers.
4) Why has not the names of character sets occuring in both
gropus been harmonized (or even better made equal)?
As stated above, the names used in the initial MIME document will be
cross refrenced to the larger set of character set names.
5) How does IANA ascertain that the same name is not allocated
to one character set in the first group of character set
names and to another in the second group?
With great care.
Olle Jarnefors Internet:
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