Have you tried using the following query?
If you are doing a UNION you don't need to have two OPTIONAL clauses inside it.
That may improve the performance, as the issue may be that the query
is being cut off after a certain amount of computation time and you
are getting partial results based on the physical file layout of the
RDF database and number of RDF statements surrounding each URI.
Also, why are you doing the negation test on the language? I thought
that all abstracts and labels in DBpedia had language tags attached to
them, so it should be okay just to do the english test.
SELECT ?label, ?abstract, ?redirect, COUNT(?wikilink)
WHERE {
{
<http://dbpedia.org/resource/$lod_id> <http://dbpedia.org/
property/abstract> ?abstract .
FILTER ( langMatches( lang(?abstract), 'en') || ! langMatches
(lang(?abstract),'*') ) .
<http://dbpedia.org/resource/$lod_id> <http://www.w3.org/2000/01/
rdf-schema#label> ?label .
FILTER ( langMatches( lang(?label), 'en') || ! langMatches(lang(?
label),'*') ) .
}
UNION
{
?redirect <http://dbpedia.org/property/redirect> <http://
dbpedia.org/resource/$lod_id> .
OPTIONAL { ?wikilink <http://dbpedia.org/property/wikilink> ?
redirect }
}
}
Cheers,
Peter
2010/1/15 David Spacey <[email protected]>:
> Hi,
>
> I'm having difficulty querying dbpedia using the sparql interface on
>
> http://dbpedia-live.openlinksw.com/sparql
>
> I'm requesting the label, abstract and a list of redirects, and
> approx. 20% of the time I'm just getting the redirects. With an
> internal instance, running an older snapshot of dbpedia, I'm seeing
> the same problem for around 1% of queries. In every example I've
> checked, the dbpedia id is still current.
>
> So, here are some examples.
>
> Failing on dbpedia-live only
> Adolf_Hitler
> Chicago
> Dora_Bryan
> Emma_Thompson
> Ferrari
>
> Failing on snapshot only
> Austriamicrosystems
> Valery_Gergiev
> Lady_Rachel_Billington
>
> Failing on both
> G20
> Darcy_Edwards
>
> This is the query I'm using, where '$lod_id' is one of the strings
> listed above.
>
> SELECT ?label, ?abstract, ?redirect, COUNT(?wikilink)
> WHERE {
> {
> <http://dbpedia.org/resource/$lod_id> <http://dbpedia.org/
> property/abstract> ?abstract .
> FILTER ( langMatches( lang(?abstract), 'en') || ! langMatches
> (lang(?abstract),'*') ) .
> <http://dbpedia.org/resource/$lod_id> <http://www.w3.org/2000/01/
> rdf-schema#label> ?label .
> FILTER ( langMatches( lang(?label), 'en') || ! langMatches(lang(?
> label),'*') ) .
> }
> UNION
> {
> OPTIONAL {
> ?redirect <http://dbpedia.org/property/redirect> <http://
> dbpedia.org/resource/$lod_id> .
> OPTIONAL { ?wikilink <http://dbpedia.org/property/wikilink> ?
> redirect }
> }
> }
> }
>
> Can anyone suggest why this might fail for valid entries?
>
> TIA
>
> Dave Spacey
>
>
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