There's really not a clean (straightforward) way to do this.

You can probably find some creative ways around it, though. Some might include:

1. if you're using -S prog, use some standard string to indicate no value for a 
property: NA or NONE or something like that. Some string that won't be likely to 
appear in valid properties.

2. search for (not a*) and (not b*) ... and (not z*)
for each of your word characters (start word characters, really). You could set 
that up as a pre-defined query. I would expect it to be really slow 
(comparatively) though, because of all the wildcards.

3. Like #1, but use a low ascii char (a control character) to indicate the 
'empty' property. Then set PropertyNamesNoStripChars config param to 'yes'.

CheHax scribbled on 6/3/05 5:16 AM:

> Hello list,
> 
> I am still working on my search engine (it is working pretty smoothly
> now and should be open in beta) and I was wondering if there is a way
> to search for an empty metatag.
> 
> Say I have 2 metas : company name and company activity.
> I want to search companies with undefined activity, and so an empty string...
> Is there a way to do so ?
> 
> Thanks
> CheHax

-- 
Peter Karman  .  http://peknet.com/  .  peter(at)not-real.peknet.com