CODEWITHSUNDEEP
sparqlwikidatafederated-queries
Jero Torralba
Jero Torralba

Reputation: 73

SPARQL Federated Queries to Wikidata from nobelprize times out

I'm trying to do a SPARQL federated query from nobelprize endpoint to Wikidata endpoint, but it returns a 502 Proxy Error.

The code:

SELECT * WHERE {
SERVICE <https://query.wikidata.org/sparql> {
    ?j ?k ?l 
  }
} LIMIT 10

Things I've tried:

  1. I've tried to do the opposite (from Wikidata to nobelprize), but it also returns another error:
SPARQL-QUERY: queryStr=select * where {
SERVICE <https://data.nobelprize.org/store/sparql/> {
    ?j ?k ?l 
  }
} LIMIT 10
  1. I've tried to do a federated query from Wikidata to DBpedia (endpoint: http://dbpedia.org/sparql) and to Europeana (endpoint: http://sparql.europeana.eu/), both work but I need to access nobelprize.

Querying DBpedia and works:

SELECT *
WHERE {
  SERVICE <http://dbpedia.org/sparql>{
  SELECT *
  WHERE{                          
    ?s ?p ?o
  }
  LIMIT 10
}

Querying Europeana and works:

SELECT *
WHERE {
   SERVICE <http://sparql.europeana.eu/>{
   SELECT *
   WHERE{                          
     ?s ?p ?o
   }
   LIMIT 10
  }  
}
  1. I've tried to use a local server (Jena), and I can query "wikidata" and "nobelprize" individually, but when entering a federated query (from either endpoint), the aforementioned errors appear.

Upvotes: 2

Views: 90

Answers (1)

Jero Torralba
Jero Torralba

Reputation: 73

I could solve the problem thanks to @UninformedUser's comment:

download the Nobel Prize Dataset dump from here, load into Fuseki, then do an efficient federated query which does select some data from the local dataset and enrich it with Wikidata via SERVICE clause

P.S., I had to download the dataset from https://www.ida.liu.se/research/semanticweb/events/SemWebCourse2018/nobelprize.nt

It worked perfectly.

Upvotes: 2

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