Hello,
On 11.10.2010 13:09, Jens Lehmann wrote:
Hello,
using the official DBpedia endpoint (http://dbpedia.org/sparql), I get
missing results on this CONSTRUCT query:
CONSTRUCT {<http://dbpedia.org/resource/Leipzig> ?p0 ?o0 .
?o0 ?p1 ?o1 .}
WHERE {<http://dbpedia.org/resource/Leipzig> ?p0 ?o0 .
OPTIONAL { ?o0 ?p1 ?o1 . } }
ORDER BY ?p0 ?o0 ?p1 ?o1
For instance, it does not contain a "populationTotal" triple. The
following simpler query contains this triple:
CONSTRUCT {<http://dbpedia.org/resource/Leipzig> ?p0 ?o0 .}
WHERE {<http://dbpedia.org/resource/Leipzig> ?p0 ?o0 . }
ORDER BY ?p0 ?o0
I thought this could be related to anytime queries, but then it's not
such a hard query (one join and "Leipzig" is a fixed resource).
Kingsley suggested me to try the same on
http://lod.openlinksw.com/sparql for shortening the problem discovery
process. The result is the same, e.g. "populationTotal" is missing from
the 2nd query result.
Here are the queries as links for your convenience:
http://lod.openlinksw.com/sparql?default-graph-uri=http%3A%2F%2Fdbpedia.org&should-sponge=&query=CONSTRUCT+{+%3Chttp%3A%2F%2Fdbpedia.org%2Fresource%2FLeipzig%3E+%3Fp0+%3Fo0+.}%0D%0AWHERE+{+%3Chttp%3A%2F%2Fdbpedia.org%2Fresource%2FLeipzig%3E+%3Fp0++%3Fo0+.+}%0D%0AORDER+BY+%3Fp0+%3Fo0%0D%0A%0D%0A&format=text%2Fplain&debug=on&timeout=
http://lod.openlinksw.com/sparql?default-graph-uri=http%3A%2F%2Fdbpedia.org&should-sponge=&query=CONSTRUCT+{+%3Chttp%3A%2F%2Fdbpedia.org%2Fresource%2FLeipzig%3E+%3Fp0+%3Fo0+.%0D%0A++++++++++++%3Fo0+%3Fp1+%3Fo1+.}%0D%0AWHERE+{+%3Chttp%3A%2F%2Fdbpedia.org%2Fresource%2FLeipzig%3E+%3Fp0++%3Fo0+.%0D%0A+++++++++OPTIONAL+{+%3Fo0+++++++%3Fp1++%3Fo1+.+}+}%0D%0AORDER+BY+%3Fp0+%3Fo0+%3Fp1+%3Fo1%0D%0A&format=text%2Fplain&debug=on&timeout=
Unless I am misunderstanding something, this looks like a serious bug.
(It also happens on our local Virtuoso installations.)
Kind regards,
Jens
--
Dipl. Inf. Jens Lehmann
Department of Computer Science, University of Leipzig
Homepage: http://www.jens-lehmann.org
GPG Key: http://jens-lehmann.org/jens_lehmann.asc
