Hmm, all right - is there any sign I could watch out for in the response;
something like the DBpedia server saying This is your result BUT something
internally timed out, so this result might be incomplete; handle with care.?
I'm wondering because normally, I wouldn't run the complete query at all. I
would prefer to run only the queries for the subsets in the first place, for
the very reason of avoiding any timeouts that are bound to happen when I add an
ORDER BY ?b clause to the query for the complete list.
Regards
Von: Joshua TAYLOR [joshuaaa...@gmail.com]
Gesendet: Mittwoch, 13. November 2013 19:11
An: Florian Haag
Cc: dbpedia-discussion@lists.sourceforge.net
Betreff: Re: [Dbpedia-discussion] Inconsistent Results: Set vs. Subset and Set
- Subset
You might be interested in this StackOverflow question in which
someone trying to enumerate properties ran two queries and got two
sets of results, but then ran the intersection of those queries and
didn't get the intersection of those sets. No definitive answer was
reached; the best guess was timeouts.
http://stackoverflow.com/q/19512255/1281433
//JT
On Wed, Nov 13, 2013 at 11:31 AM, Florian Haag
florian.h...@vis.uni-stuttgart.de wrote:
Hello,
I am trying to retrieve a list of predicates from DBpedia with a SPARQL
query. The full set looks fine:
SELECT DISTINCT ?b
WHERE {
?a ?b ?c.
}
LIMIT 50
On http://dbpedia.org/sparql, this returns 50 URIs (let's call this set A),
so there are 50 (or probably more) predicates available.
Now, I just want a subset of this, namely only predicates whose last part in
the URI starts with a letter from A to Z:
SELECT DISTINCT ?b
WHERE {
?a ?b ?c.
FILTER(regex(str(?b), [/#][a-z][^/#]*$, i)).
}
LIMIT 50
This returns a surprisingly small set (let's call this set B) consisting of
only one URI (http://www.w3.org/1999/02/22-rdf-syntax-ns#type), which had
also been in set A. But if that set is so small, the complementary set should
contain at least the 49 items from set (A - B):
SELECT DISTINCT ?b
WHERE {
?a ?b ?c.
FILTER(regex(str(?b), [/#][^a-z/#][^/#]*$, i)).
}
LIMIT 50
I would expect the result set of this query to contain, for example,
http://www.w3.org/2002/07/owl#sameAs, which was contained in set A. Instead,
the result set of this last query (set C) is empty.
Why does DBpedia behave like that; is there anything wrong about my queries
or my regular expressions? (When trying this on some other endpoints
(http://vocabulary.semantic-web.at/PoolParty/sparql/AustrianSkiTeam ,
http://spatial.ucd.ie/lod/sparql ), the result seems to be as expected.) Note
that DBpedia's SPARQL web-frontend does not report any syntax errors, server
errors or timeouts.
Thanks in advance
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