sparql using wikiPageRedirects

Question

I am using sparql to find a location of entity. I have urls from dbpedia-spootlight and want to find location for them. So the query I am using is:

PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#> 
PREFIX dbo: <http://dbpedia.org/ontology/> 
SELECT DISTINCT * 
WHERE { ?uri rdfs:label ?label . 
OPTIONAL { ?uri geo:lat ?lat . ?uri geo:long ?long } . 
OPTIONAL { ?uri dbpedia-owl:country ?dbpediaContry . ?dbpediaContry dbpprop:cctld ?ccTLD } . 
FILTER (?uri = <URL>  && lang(?label) = "en" ) }

and it was fine until I have got this url: http://dbpedia.org/resource/Valencia,_Spain . It has wikiPageRedirects to http://dbpedia.org/resource/Valencia and no other data. I have got lost how could i build query to check cases with redirects.

Can anybody help me?

Btw your use of prefixes and prefixed names is very inconsistent, as written your query really should be rejected as invalid because you've used undefined prefixes — RobV, Sep 25 '12 at 23:20
yeah that's true. anyway I still play with it so didn´t really care about that. anyway it is good point. thanks — Piotr Idzikowski, Sep 26 '12 at 07:13

RobV · Accepted Answer · 2012-09-25T23:22:34.833

Try changing the first part of your query to use a UNION e.g.

PREFIX geo: <http://www.w3.org/2003/01/geo/wgs84_pos#> 
PREFIX dbo: <http://dbpedia.org/ontology/> 
PREFIX dbp: <http://dbpedia.org/property/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>

SELECT DISTINCT * 
WHERE
{ 
  { 
    ?uri rdfs:label ?label . 
  } 
  UNION 
  { 
    [] dbo:wikiPageRedirects ?uri .
    ?uri rdfs:label ?label .
  }
  OPTIONAL 
  { 
    ?uri geo:lat ?lat ;
         geo:long ?long 
  }
  OPTIONAL 
  {
    ?uri dbo:country ?dbpediaContry . 
    ?dbpediaContry dbp:cctld ?ccTLD 
  }
  FILTER (SAMETERM(?uri, <URL>)  && lang(?label) = "en" ) 
}

The UNION allow you to find things that have a URI and those that have a URI via a redirect before then applying the rest of your query. Note I also changed your FILTER to use SAMETERM() which should make the query faster.

In general if you have this kind of query where you are doing that sort of a FILTER to set a constant I would strongly suggest just replacing all uses of the ?uri variable with <URL> instead which should see much better performance

score 0 · Answer 2 · answered Sep 25 '12 at 08:53

Hmm, I have found a solution but I don´t think it is perfect. I added additional columns:

...
OPTIONAL { ?uri  dbpedia-owl:wikiPageRedirects ?red } .
OPTIONAL { ?red geo:lat ?rlat . ?red geo:long ?rlong } 
...

but now I have 2 columns more to check in response.

Another way I was trying is:

...
OPTIONAL { ?uri  dbpedia-owl:wikiPageRedirects ?red } .
{?uri geo:lat ?lat . ?uri geo:long ?long}  UNION  { ?red geo:lat ?lat . ?red geo:long ?long }
...

but then i have any answer if entity doesn´t have geo:long & geo:lat

So, anybody knows better solution?

sparql using wikiPageRedirects

2 Answers2

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