Subject: [NNTP] References Command

From: Fabian <[email-masked]>
Date: Wed, 9 Nov 2011 18:12:44 +0100

Is there a simple way to return a list of articles referencing a certain
article?

Currently, when I receive an article number, and want to fetch the articles
referencing it, I have to do a full XOVER on all groups that may possibly
contain a reply to that article. It's very inefficient, but it seems the
only way. The only alternative would be: 'XPAT References <msgid>', but a
very large percentage of the newsservers don't support XPAT because it uses
too much CPU. If there was a command like 'REFERENCES <msgid>', servers
could implement it much more efficiently than XPAT, since wildcards (*)
aren't allowed, so all it needs is a single hash-table.

Is there a specific reason why such a command doesn't exist? Or is it very
unusual for replies to be posted to a different group than the original
article?

---

From: "Jeffrey M. Vinocur" <[email-masked]>
Date: Wed, 9 Nov 2011 15:14:49 -0500 (EST)

On Wed, 9 Nov 2011, Fabian wrote:

> article? [...]

There is not (in the standard, or within INN, although perhaps some other 
server software supports this).

> [...] If there was a command like 'REFERENCES <msgid>', servers

Yes, for a single point in time.  But I think there are critical but 
subtle issues as you let time pass.  For example, when would the forward 
links expire?  If you expire them when the parent article expires, then 
you do not provide a reliable way to find siblings of a given article (by 
going to the parent and then looking at its children) once the parent has 
expired.

> Is there a specific reason why such a command doesn't exist?

Most newsreaders added offline reading and client-side threading many 
years ago (see e.g. http://www.jwz.org/doc/threading.html) and thus this 
is not a feature in much demand.

> Or is it very unusual for replies to be posted to a different group than 
> the original article?

This certainly happens from time to time; often (but not always) there is 
a transitional article that is crossposted to both groups.

My experience is that many newsreaders simply do not allow you to follow 
references forward across groups.

-- 
Jeffrey M. Vinocur
[email-masked]