Re: Simple example of need for negation operator

Hi Lee,

OK, we'll try sparql dev, as long as this is a how to, rather than a "can't
be
done".  But it looks to me like
your query returns no bindings if an article does not have a timetag.  I
say this because of the {?a ex:timetag ?maxtime} clause
that comes before the OPTIONAL.  But in that case, it should return
the article.  Can you fix this, or is it not expressible after all?

>
> In SPARQL, this query is (unedited, untested):
>
> SELECT ?a
> FROM :model
> WHERE {
>   ?a rdf:type ft:article ; ex:timetag ?maxtime .
>   OPTIONAL { ?a ex:timetag ?othertime . FILTER(?othertime > ?maxtime) }
>   FILTER (!bound(?othertime) && ?maxtime > '...now...')
> }
>
> Original target:


SELECT ?a
FROM model
WHERE
     (?a rdf:type ft:Article) AND
     UNSAID ((?a ex:timetag ?time) AND
                   (?time > $NOW))

=====================================
Robert MacGregor
Chief Scientist
Siderean Software, Inc.
bob.macgregor@gmail.com
Mobile: 310-469-2810
=====================================