[NNTP] References Command

[Jeffrey M. Vinocur]

On Wed, 9 Nov 2011, Fabian wrote:

> Is there a simple way to return a list of articles referencing a certain
> 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
> could implement it much more efficiently than XPAT, since wildcards (*)
> aren't allowed, so all it needs is a single hash-table.

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
jeff at litech.org