Dear all,
I'm running Virtuoso OS 7.1.0 and trying to run some federated queries to
DBpedia and Europeana. Here's an example of what I'm trying to do (fetch
some Europeana artifacts created during the lifetime of Ghandi, as a
simplified example):
prefix db: <http://dbpedia.org/ontology/>
prefix dc: <http://purl.org/dc/elements/1.1/>
prefix xsd: <http://www.w3.org/2001/XMLSchema#>
SELECT * WHERE {
SERVICE <http://dbpedia.org/sparql> {
<http://dbpedia.org/resource/Mahatma_Gandhi> db:birthDate ?birth ;
db:deathDate ?death .
}
SERVICE <http://europeana.ontotext.com/sparql> {
SELECT * WHERE {
?artifact dc:date ?date .
FILTER ( ?date >= xsd:string(?birth) && ?date <= xsd:string(?death) )
} LIMIT 10
}
} LIMIT 10
If I run this through the sparql.org endpoint, it works without problems
[1]. Virtuoso gives me the following error, though:
Virtuoso 37000 Error SP031: SPARQL compiler: Variable 'birth' is used
in the query result set but not assigned
Is this a know limitation of Virtuoso?
Thanks,
Carsten
[1]
http://sparql.org/sparql?query=prefix+db%3A+%3Chttp%3A%2F%2Fdbpedia.org%2Fontology%2F%3E%0D%0Aprefix+dc%3A+%3Chttp%3A%2F%2Fpurl.org%2Fdc%2Felements%2F1.1%2F%3E%0D%0Aprefix+xsd%3A+%3Chttp%3A%2F%2Fwww.w3.org%2F2001%2FXMLSchema%23%3E%0D%0A%0D%0ASELECT+*+WHERE+%7B%0D%0A%0D%0A%09SERVICE+%3Chttp%3A%2F%2Fdbpedia.org%2Fsparql%3E+%7B+%0D%0A%09%09+%3Chttp%3A%2F%2Fdbpedia.org%2Fresource%2FMahatma_Gandhi%3E+db%3AbirthDate+%3Fbirth+%3B%0D%0A+++++++++++++++++++++++++++++db%3AdeathDate+%3Fdeath+.%0D%0A%0D%0A%09%7D%0D%0A%0D%0A+++++++SERVICE+%3Chttp%3A%2F%2Feuropeana.ontotext.com%2Fsparql%3E+%7B+%0D%0A++++++++++++SELECT+*+WHERE+%7B%0D%0A%09%09%3Fartifact+dc%3Adate+%3Fdate+.%0D%0A%09%09FILTER+%28+%3Fdate+%3E%3D+xsd%3Astring%28%3Fbirth%29+%26%26+%3Fdate+%3C%3D+xsd%3Astring%28%3Fdeath%29+%29++%09%0D%0A+++++++++++%7D+LIMIT+10%09%0D%0A%09%7D%0D%0A++++++++%0D%0A%7D+LIMIT+10&default-graph-uri=http%3A%2F%2Fdbpedia.org%2Fdata%2FMahatma_Gandhi.rdf&output=text&stylesheet=%2Fxml-to-html.xsl
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