[NNTP] LISTGROUP

[Charles Lindsey]

In <20050325125918.GI47012 at finch-staff-1.thus.net> "Clive D.W. Feather" <clive at demon.net> writes:

>Not in a newsgroup name.

>The formal syntax uses special non-terminals S-CHAR, S-NONTAB, and S-TEXT
>that have two separate definitions: one that MUST be accepted, and one that
>SHOULD be generated.
>* Header content in articles (when unfolded) is S-CHAR.
>* Header contents in HDR/OVER responses is S-NONTAB.
>* Newsgroup description is S-TEXT.
>Apart from article bodies and the HELP output, the entire remaining syntax
>is UTF-8 based.

>For the record:

>                  MUST accept                 SHOULD generate
>    S-CHAR        %x21-FF                     any UTF-8 from U+0021 upwards
>    S-NONTAB      any except TAB              any UTF-8 except TAB
>    S-TEXT        any but not beginning       any UTF-8, but beginning
>                  with TAB or SP              with U+0021 or above

>(in all the above, "any" excludes NUL, CR, and LF).

Now I am even more confused, because one has to define carefully when
"accept" applies and when "generate" applies.

Suppose "!@#$" represents some sequence of octets not allowed within
UTF8-non-ascii, and suppose it is used in headers by some Chinese system
that insists on using Big-8 (or whatever the Chinese charset is called) in
defiance of all the format standards.

So an article is POSTed containing the header "Subject: !@#$". That is a
"MUST accept", so the server accepts it. What does the server then do with
it? That is not really our business, but having accepted it we should not
be surprised if it stores it and/or attempts to relay it to other sites.

So the server has stored it, and now some other client tries to READ it.
Are you saying that your "SHOULD generate" is violated if the article is
now sent, including that "!@#$", in response to the READ. Likewise, is that
"SHOULD generate" violated if the server becomes a client and says IHAVE
that article to another server, and then sends it as-is (in which case
it is a "MUST accept" for the other site).

For sure, things get a little more interesting if this header gets
involved in the response to an OVER or HDR command. But even there, if the
server naively includes that "!@#$" in the proper place within the
response, is that "SHOULD generate" violated?

In fact, I think it is clear that all existing implementations will simply
include that "!@#$" in all the relevant places, simply because it it too
much hassle and a waste of resources to try and detect these obscure
happenings (and observe that the "!@#$" is perfectly acceptable in bodies
given a suitable Content-Type header).

-- 
Charles H. Lindsey ---------At Home, doing my own thing------------------------
Tel: +44 161 436 6131 Fax: +44 161 436 6133   Web: http://www.cs.man.ac.uk/~chl
Email: chl at clerew.man.ac.uk      Snail: 5 Clerewood Ave, CHEADLE, SK8 3JU, U.K.
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