Hi,
perhaps some more information is needed in order to understand why I'm
getting this?
I don't know if it can be useful to check the actual dataset: it's a
partial dataset obtained by querying the Revyu SPARQL endpoint
Best,
Alessandro
On 1/31/12 12:12 PM, Alessandro Adamou wrote:
Hi, I tried to execute this query - path of length 2 - on a partial
dump of Revyu, using a JenaSparqlEngine registered with QueryParser:
SELECT ?r0 ?x0 ?r1
WHERE {
<http://semanticweb.org/dumps/people/teddypolar> ?r0 ?x0 .
?x0 ?r1
<http://semanticweb.org/dumps/things/alcazar-food-fun-and-music-in-paris>
}
and got the RuntimeException whose partial trace is attached at the
end of this message:
java.lang.RuntimeException: cannot convert
"dcc31c09026e5a3aee0b63cb44a07ff8a76d1449" to NonLiteral
Indeed it is because the value
"dcc31c09026e5a3aee0b63cb44a07ff8a76d1449" (for ?x0) is an untyped
literal, so no paths con be constructed there. Still I hoped datatype
and annotation assertions would be skipped instead of throwing
exceptions.
So I thought I could just make the second step in the path OPTIONAL -
after all I need shorter paths too - like this:
SELECT ?r0 ?x0 ?r1
WHERE {
<http://semanticweb.org/dumps/people/teddypolar> ?r0 ?x0
OPTIONAL {
?x0 ?r1
<http://semanticweb.org/dumps/things/alcazar-food-fun-and-music-in-paris>
}
}
... but I just get the same exception.
This very same query (with OPTIONAL) on other SPARQL engines, such as
the TopBraid Composer one, terminates and delivers the expected results.
Is there a clue as to how this query can be executed "safely", without
forcing conversion of literals?
Thanks!
Alessandro
------- EXCEPTION TRACE FOLLOWS --------
java.lang.RuntimeException: cannot convert
"dcc31c09026e5a3aee0b63cb44a07ff8a76d1449" to NonLiteral
at
org.apache.clerezza.rdf.jena.commons.Jena2TriaUtil.convertNonLiteral(Jena2TriaUtil.java:127)
at
org.apache.clerezza.rdf.jena.facade.JenaGraph.filter(JenaGraph.java:123)
at
org.apache.clerezza.rdf.jena.facade.JenaGraph.graphBaseFind(JenaGraph.java:151)
at com.hp.hpl.jena.graph.impl.GraphBase.find(GraphBase.java:240)
at
com.hp.hpl.jena.graph.impl.GraphBase.graphBaseFind(GraphBase.java:260)
at com.hp.hpl.jena.graph.impl.GraphBase.find(GraphBase.java:257)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIterTriplePattern$TripleMapper.<init>(QueryIterTriplePattern.java:67)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIterTriplePattern.nextStage(QueryIterTriplePattern.java:41)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.makeNextStage(QueryIterRepeatApply.java:91)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:52)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:66)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIterBlockTriples.hasNextBinding(QueryIterBlockTriples.java:53)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:66)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIterDefaulting.hasNextBinding(QueryIterDefaulting.java:43)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:66)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIterRepeatApply.hasNextBinding(QueryIterRepeatApply.java:57)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:66)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIterConvert.hasNextBinding(QueryIterConvert.java:49)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:66)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:28)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:66)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorWrapper.hasNextBinding(QueryIteratorWrapper.java:28)
at
com.hp.hpl.jena.sparql.engine.iterator.QueryIteratorBase.hasNext(QueryIteratorBase.java:66)
at
com.hp.hpl.jena.sparql.engine.ResultSetStream.hasNext(ResultSetStream.java:57)
at
org.apache.clerezza.rdf.jena.sparql.ResultSetWrapper.<init>(ResultSetWrapper.java:39)
at
org.apache.clerezza.rdf.jena.sparql.JenaSparqlEngine.execute(JenaSparqlEngine.java:68)
at
org.apache.clerezza.rdf.core.access.TcManager.executeSparqlQuery(TcManager.java:272)
--
M.Sc. Alessandro Adamou
Alma Mater Studiorum - Università di Bologna
Department of Computer Science
Mura Anteo Zamboni 7, 40127 Bologna - Italy
Semantic Technology Laboratory (STLab)
Institute for Cognitive Science and Technology (ISTC)
National Research Council (CNR)
Via Nomentana 56, 00161 Rome - Italy
"As for the charges against me, I am unconcerned. I am beyond their timid, lying
morality, and so I am beyond caring."
(Col. Walter E. Kurtz)
Not sent from my iSnobTechDevice
