sparql using wikiPageRedirects

问题:

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?

回答1:

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

回答2:

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?