ietf-nntp OVER extension

[greg andruk]

On Wed, Jan 02, 2002 at 09:36:43AM +0000, Clive D.W. Feather wrote:
> greg andruk said:
> >>> But if (5) is agreed, then the whole LIST OVERVIEW.FMT command becomes
> >>> redundant, as Greg Andruk has said.
> >> Not so. It allows you to determine what headers will be provided and,
> >> therefore, which ones are missing from any given response. Without it, how
> >> can you tell whether X-Wombat is included in the overview (and your probings
> >> so far have been unlucky) or not ?
> > All extension headers include the name, so you know for each and every line
> > of output what headers are included or omitted.
> 
> You've missed my point.

No, but there are enough buggy overview generators out there that could lead
you to believe otherwise.

> How do I know whether X-Wombat is included in the OVER output ? I can't
> find out by using OVER on random articles, because I might be unlucky and
> never hit an article with one in it. The only way to be *sure* is to look
> at the LIST OVERVIEW.FMT output.

In a correct NOV implementation, only two fields (lines and references) are
allowed to be blank.  All of the labeled fields must include labels, though
of course there will only be text after the colon if the article contains
some.  The one exception is that if _all_ the extension fields are blank,
then all of the tabs following the unlabeled fields may be omitted.

The original NOV implementation only included one sample extension field
(xref), so that the source code may not have adequately highlighted the
all-or-nothing nature of extension labels.  That information was only driven
home in the man page.  I've uploaded an HTML-formatted copy of the document
to <URL:http://members.verizon.net/~vze35rzk/nntpext/newsoverview.5.html>
for reference.

I will again note that overview.fmt _does_ _not_ tell the client what
headers have already been collected in the overview.  It describes what
fields will be added in the immediate future, and it may or may not
correspond to the contents of records stored before today.