[redland-dev] query range in SPARQL

[Andre Meyer]

Wow, that's wonderful! The devil's in the details...

In order to find the neighbours within a given distance I added the
FILTER as follows:

x0 = 50
y0 = 50
d = 25
q = RDF.SPARQLQuery("""PREFIX  di: <http://python.openspace.nl/di#>
SELECT  ?s ?x ?y
WHERE
 { ?s  di:x  ?x ;
       di:y  ?y .
       FILTER ((?x-%s)*(?x-%s) + (?y-%s)*(?y-%s) < %s*%s) .
 }""" % (x0, x0, y0, y0, d, d))


thanks!
Andre


On 10/5/06, Seaborne, Andy <andy.seaborne at hp.com> wrote:
>
> The query has:
>
> { (?s di:x ?x) . (?s di:y ?y) . }
>
> but in SPARQL triple patterns aren't delimited by ().  Unfortunately, in
> SPARQL, () are RDF lists and your query really looks like:
>
>
> PREFIX  di: <http://python.openspace.nl/di#>
> PREFIX  rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> # Added for
> clarity
>
> SELECT  ?s ?x ?y
> WHERE
>   { _:b0  rdf:first  ?s ;
>           rdf:rest   _:b1 .
>     _:b1  rdf:first  di:x ;
>           rdf:rest   _:b2 .
>     _:b2  rdf:first  ?x ;
>           rdf:rest   rdf:nil .
>     _:b3  rdf:first  ?s ;
>           rdf:rest   _:b4 .
>     _:b4  rdf:first  di:y ;
>           rdf:rest   _:b5 .
>     _:b5  rdf:first  ?y ;
>           rdf:rest   rdf:nil .
>   }
>
> which may not be what you intended.
>
> If the () are removed, then the query is:
>
> PREFIX  di: <http://python.openspace.nl/di#>
>
> SELECT  ?s ?x ?y
> WHERE
>   { ?s  di:x  ?x ;
>         di:y  ?y .
>   }
>
> http://www.sparql.org/validator.html
>
>         Andy
>
> -------- Original Message --------
> > From: Andre Meyer <>
> > Date: 4 October 2006 19:25
> >
> > That's a good one!!! Hope this works for all kinds of functions one
> > might want to use.
> >
> > Nevertheless, I still can't manage to query properly. Trying to use
> the
> > Python example I got the attached file, which finds nothing, with or
> > without filter.
> >
> > thanks
> > Andre
>



-- 
Dr. Andre P. Meyer                        http://python.openspace.nl/meyer
TNO Defence, Security and Safety          http://www.tno.nl/
Delft Cooperation on Intelligent Systems  http://www.decis.nl/

Ah, this is obviously some strange usage of the word 'safe' that I
wasn't previously aware of. - Douglas Adams