Hi everyone,
I've found a strange behaviour when executing a SPARQL query having
GROUP_CONCAT on a Jena-Fuseki SPARQL endpoint.
Executing, for example, the following query:
SELECT DISTINCT ?resource (GROUP_CONCAT( ?singleLabel; separator=",")
AS ?multiLabel )
WHERE {
?resource a <http://www.w3.org/2004/02/skos/core#Concept> .
?resource (<http://www.w3.org/2008/05/skos-xl#prefLabel> |
<http://www.w3.org/2008/05/skos-xl#altLabel>) ?skosxlLabel .
?skosxlLabel <http://www.w3.org/2008/05/skos-xl#literalForm>
?singleLabel .
FILTER regex(str(?singleLabel), 'dog', 'i')
}
GROUP BY ?resource
on the AGROVOC SPARQL endpoint at
http://agrovoc.uniroma2.it:3030/agrovoc/sparql (it's using
apache-jena-fuseki-3.6.0 and it has no GUI, so you need to use another
GUI, for example http://yasgui.org/ ) you get no answer, unless you do
such query from one of Tor Vergata IPs (Tor Vergata is hosting such
SPARQL endpoint).
If I remove
(GROUP_CONCAT( ?singleLabel; separator=",") AS ?multiLabel )
then I'm able to execute such query from every where.
Does any of you know why I get such strange behaviour? How can I fix the
problem (apart from doing a SPARQL query without the GROUP )
Thank you for your answer
Cheers
Andrea
--
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Dott. Andrea Turbati, PhD
AI Research Group,
Dept. of Enterprise Engineering
University of Roma, Tor Vergata
Via del Politecnico 1 00133 ROMA (ITALY)
tel: +39 06 7259 7334
lab: +39 06 7259 7332
e_mail: turb...@info.uniroma2.it
home page: http://art.uniroma2.it/turbati/
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