SHOULD we include charset=ISO-8859-1?

Misha Wolf (misha.wolf@reuters.com)
Tue, 18 Feb 1997 17:30:06 +0000 (GMT) 

We are having trouble understanding these paragraphs taken from RFC 2068 
(HTTP/1.1):

   The "charset" parameter is used with some media types to define the
   character set (section 3.4) of the data. When no explicit charset
   parameter is provided by the sender, media subtypes of the "text"
   type are defined to have a default charset value of "ISO-8859-1" when
   received via HTTP. Data in character sets other than "ISO-8859-1" or
   its subsets MUST be labeled with an appropriate charset value.

   Some HTTP/1.0 software has interpreted a Content-Type header without
   charset parameter incorrectly to mean "recipient should guess."
   Senders wishing to defeat this behavior MAY include a charset
   parameter even when the charset is ISO-8859-1 and SHOULD do so when
   it is known that it will not confuse the recipient.

   Unfortunately, some older HTTP/1.0 clients did not deal properly with
   an explicit charset parameter. HTTP/1.1 recipients MUST respect the
   charset label provided by the sender; and those user agents that have
   a provision to "guess" a charset MUST use the charset from the
   content-type field if they support that charset, rather than the
   recipient's preference, when initially displaying a document.

1. Could the person who wrote "... when it is known that it will not confuse 
the recipient." please explain the circumstances under which a recipient 
may be confused as a result of the sender including a charset parameter.

2. How are we to parse the entire sentence "Senders wishing to defeat this 
behavior MAY include a charset parameter even when the charset is ISO-8859-1 
and SHOULD do so when it is known that it will not confuse the recipient."?

Is it only senders who wish "to defeat this behaviour" who "SHOULD do so"?
Or does the "SHOULD" apply to all senders?

We have studied the definitions of "MAY" and "SHOULD" in section 1.2, and 
are unclear whether the meaning of these terms is, in this instance, modified 
by the introductory words "Senders wishing to defeat this behavior".

misha.wolf@reuters.com
charles.wicksteed@reuters.com