Hello Lorenz,
Both queries are correct and results looks correct, but these are two
different queries. For variant with !BOUND you need an OPTIONAL, without
OPTIONAL all variables from triple patterns are bound in every result by
definition.
SELECT DISTINCT ?x0 WHERE{
?x0 <http://dbpedia.org/ontology/position> ?x7.
?x0 <http://purl.org/dc/terms/subject>
<http://dbpedia.org/resource/Category:Premier_League_clubs>.
?x0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://dbpedia.org/class/yago/PremierLeagueClubs>.
OPTIONAL {?x0 <http://dbpedia.org/property/league> ?x8.}
filter (!bound (?x8))
} LIMIT 10
returns one http://dbpedia.org/resource/Wimbledon_F.C. as well.
Best Regards,
Ivan Mikhailov
OpenLink Software
http://virtuoso.openlinksw.com
On Sun, 2011-06-26 at 23:17 +0200, Lorenz Buehmann wrote:
> Hi,
>
> i'm not sure whether it is a bug, but i hope you can explain me the
> behaviour. To me it sounds like the following 2 queries should return
> the same result:
>
> Query 1:
>
> SELECT DISTINCT ?x0 WHERE{
> ?x0 <http://dbpedia.org/ontology/position> ?x7.
> ?x0 <http://purl.org/dc/terms/subject>
> <http://dbpedia.org/resource/Category:Premier_League_clubs>.
> ?x0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
> <http://dbpedia.org/class/yago/PremierLeagueClubs>.
> FILTER(
> (!bif:exists((
> SELECT * WHERE {?x0 <http://dbpedia.org/property/league> ?x8.}
> )))
> )
> } LIMIT 10
>
> Query 2:
>
> SELECT DISTINCT ?x0 WHERE{
> ?x0 <http://dbpedia.org/ontology/position> ?x7.
> ?x0 <http://purl.org/dc/terms/subject>
> <http://dbpedia.org/resource/Category:Premier_League_clubs>.
> ?x0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
> <http://dbpedia.org/class/yago/PremierLeagueClubs>.
> ?x0 <http://dbpedia.org/property/league> ?x8.
> FILTER(!BOUND(?x8))
> } LIMIT 10
>
> When i execute this queries on http://dbpedia.org/sparql i get 1 result
> for query 1, but no result for query 2. Is this correct?
>
>
>
> There is also a difference in the results when i compare query 1 with
> another query 3 on http://live.dbpedia.org/sparql , because executing
> query 1 returns no result, but if i change the order of the triple pattern,
> then i get some result.
>
> Query 3:
>
> SELECT DISTINCT ?x0 WHERE{
> ?x0 <http://purl.org/dc/terms/subject>
> <http://dbpedia.org/resource/Category:Premier_League_clubs>.
> ?x0 <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
> <http://dbpedia.org/class/yago/PremierLeagueClubs>.
> ?x0 <http://dbpedia.org/ontology/position> ?x7.
> FILTER(
> (!bif:exists((
> SELECT * WHERE {?x0 <http://dbpedia.org/property/league> ?x8.}
> )))
> )
> } LIMIT 10
>
> By the way, on http://live.dbpedia.org/sparql query 2 and 3 return also
> not the same result.
>
>
> Maybe one of the developers can explain this all to me. Thanks in advance.
>
>
> Regards,
> Lorenz
>
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