Hi !!
I have a problem with the following query :
select *where { ?sensor rdf:type km4c:SensorSite. ?sensor
dcterms:identifier 'FI055ZTL00901'. SERVICE <http://localhost:2020/sparql>{
SELECT ?sensor ?obs { ?obs km4c:isObservationOf
?sensor. } limit 10 }}
I get the following error:
Virtuoso RDFZZ Error DB.DBA.SPARQL_REXEC('http://localhost:2020/sparql', ...)
returned Content-Type 'text/html' status 'HTTP/1.1 400 Parse error: SELECT
?obs WHERE { ?obs . FILTER (isREF ( )) } Lexical error at line 3,
column 19. Encountered: " " ('
Error 400 Parse error:
SELECT ?obs
WHERE { ?obs .
FILTER (isREF ( )) }
Lexical error at line 3, column 19. Encountered: " " (32), after : "isREF"
HTTP ERROR 400
Problem accessing /sparql. Reason:
Parse error:
SELECT ?obs
WHERE { ?obs .
FILTER (isREF ( )) }
Lexical error at line 3, column 19. Encountered: " " (32), after :
"isREF"Powered by Jetty://
The server running at http://localhost:2020 is a D2R server and
http://localhost:2020/sparql is a SPARQL endpoint.Initially I thought it was
just a D2R error, but the strange thing is that if I select only ?obs inside
the SERVICE clause, that is if I run the following query :select *where {
?sensor rdf:type km4c:SensorSite. ?sensor dcterms:identifier
'FI055ZTL00901'. SERVICE <http://localhost:2020/sparql>{ SELECT
?obs { ?obs km4c:isObservationOf ?sensor. } limit
10 }}I get the correct result. The problem with the latter query is that
the variable sensor seems not bound to any value when the graph pattern inside
the SERVICE clause is matched in D2R. That's why I'd prefer the former
solution. The variable sensor should be bound to an IRI.If I run the former
query from Fuseki server I get the correct result, so I was wondering why I'm
not able to run it from Virtuoso.Maybe can't I query a D2R endpoint from a
Virtuoso endpoint?Or do you think the problem is in D2R?
Thanks a lot for your help and your time.
Best Regards,Francesco Balzano.
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