Hi Hyrundo,
The query as written is executed locally, and when execution reaches the
SERVICE clauses the engine calls out to the named service.
Instead of:
QueryExecutionFactory.sparqlService
use
QueryExecutionFactory.create
Andy
On 27/11/2019 16:23, Hyrundo Publishing Association wrote:
Hello Sirs at Jena,
I am following the examples of federated queries given at this URL:
https://www.oclc.org/developer/news/2016/federated-queries-with-sparql.en.html
<https://www.oclc.org/developer/news/2016/federated-queries-with-sparql.en.html>
and then I’m trying to replicate the results bringing those SPARQL examples
into a Jena/Java Main class in NetBeans…
with no results…
For example, the given SPARQL code:
PREFIX schema: <http://schema.org/>
PREFIX library: <http://purl.org/library/>
PREFIX wdt: <http://www.wikidata.org/prop/direct/>
PREFIX dct: <http://purl.org/dc/terms/>
SELECT ?work ?workLabel
FROM <http://www.worldcat.org/oclc/470488115>
WHERE {
<http://www.worldcat.org/oclc/470488115> schema:author ?creatorURI.
BIND(replace(STR(?creatorURI), "^(.*[\\/])*", "") AS ?creatorID)
{SERVICE <https://query.wikidata.org/sparql> { //endpoint n.1
?author wdt:P214 ?creatorID.
?work wdt:P50 ?author .
? work wdt:P1476 ?workLabel
}
}
UNION
{
SERVICE <http://bnb.data.bl.uk/sparql> { //endpoint n.2
?bl_creator ?creatorURI.
?work dct:creator ?bl_creator.
?work dct:title ?workLabel
}
}
}
When having two different endpoints to query, how to set the query execution in
Jena?
Query query = QueryFactory.create(queryStr);
QueryExecution qexec =
QueryExecutionFactory.sparqlService(“http://URL_of_the_SPARQL_endpoint";, query)
?
Any hint?
Thank you in advance.
Hyrundo
