Re: virtual nnvirtual

[Andrew Cohen <acohen@ust.hk>]

>>>>> "ESF" == Eric S Fraga <e.fraga@ucl.ac.uk> writes:

    ESF> Andrew, a quick question: what should a virtual group based on
    ESF> nnselect give me that the normal virtual groups do not, if
    ESF> anything?

Umm, not totally sure? The main thing is that it uses the up-to-date,
properly maintained part of the code as opposed to something that I
don't think has been touched in a long time ;-) (Seriously, looking
at the log it seems the last real  change to the code is from well over
a decade ago). Also, it doesn't special-case anything---nnselect is very
generic and nnvirtual comes "for free" (just a single function to
generate the article list).

But specifically you should get:

    ESF> 1. /o to return the right set of articles from the set of
    ESF> constituent groups.  

I'm not sure what "the right set" means---this function prompts for a
number of old articles and returns them, which the nnselect version
should do (and does in my minimal tests). As to which articles are
returned, it is (currently) the set defined by the nnvirtual
algorithm---starting from most recent to oldest, return one from the
first group, one from the second, etc, cycling through the groups; once
any group is exhausted just skip it in further cycles. We can easily
change this to something else if this isn't what is desired.

    ESF> 2. A T to work as well, collecting articles from different
    ESF> groups.

This should work (provided searching is configured for the constituent
groups).

In addition you get all the functionality of nnselect----this means that
it will behave as any other nnselect group (marks are propagated to and
from the constituent groups, you can search the whole group, you can
refer articles, you can use article expiry, etc). In fact I don't think
there is anything that a real group does that nnselect doesn't (if there
is, I guess that should be considered a bug). I don't really know if
nnvirtual does everything as well, but my memory from a decade ago when
I looked at it is it doesn't implement everything. But I might be
mis-remembering.


-- 
Andrew Cohen