Re: Basic federation in Jena
Oops, the webpage I mentionned had wrong code.
The correct code to run my query is:
QueryExeuction exec =
QueryExecutionFactory.create(QueryFactory.create(yourfederatedquery,
Syntax.syntaxARQ), new
DatasetImpl(ModelFactory.createDefaultModel()));
exec.execSelect();
Forcing the syntax to Syntax.syntaxARQ is mandatory because
client-side federation is a ARQ-specific feature.
On Tue, Jul 31, 2012 at 9:40 AM, Olivier Rossel
olivier.ros...@gmail.com wrote:
Hi all.
I would like to try Jena basic federation.
I tried this query:
SELECT DISTINCT ?thCenturyClassicalComposers0 WHERE { SERVICE
http://api.talis.com/stores/bbc-backstage/services/sparql {
?thCenturyClassicalComposers0
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
http://dbpedia.org/class/yago/20thCenturyClassicalComposers .
}} LIMIT 300
with the code provided here:
cf http://tech.groups.yahoo.com/group/jena-dev/message/48130
I get some results.
Now I try this query:
SELECT DISTINCT ?thCenturyClassicalComposers0 ?comment WHERE { SERVICE
http://api.talis.com/stores/bbc-backstage/services/sparql
{?thCenturyClassicalComposers0
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
http://dbpedia.org/class/yago/20thCenturyClassicalComposers .
} SERVICE http://dbpedia.org/sparql {?thCenturyClassicalComposers0
http://www.w3.org/2000/01/rdf-schema#comment ?comment} } LIMIT 300
I get no result.
But when checking data on each endpoint, I should get some results.
Is there something wrong in my SPARQL SERVICE syntax?
BTW, being able to limit/offset/orderBy and OPTIONALize each SERVICE
block would be uber nice ! ! ! Is it possible already?
Re: Basic federation in Jena
On 31/07/12 08:52, Olivier Rossel wrote:
Oops, the webpage I mentionned had wrong code.
The correct code to run my query is:
QueryExeuction exec =
QueryExecutionFactory.create(QueryFactory.create(yourfederatedquery,
Syntax.syntaxARQ), new
DatasetImpl(ModelFactory.createDefaultModel()));
exec.execSelect();
Forcing the syntax to Syntax.syntaxARQ is mandatory because
client-side federation is a ARQ-specific feature.
Only in very old versions of ARQ - SERVICE is part of SPARQL 1.1
On Tue, Jul 31, 2012 at 9:40 AM, Olivier Rossel
olivier.ros...@gmail.com wrote:
Hi all.
I would like to try Jena basic federation.
I tried this query:
SELECT DISTINCT ?thCenturyClassicalComposers0 WHERE { SERVICE
http://api.talis.com/stores/bbc-backstage/services/sparql {
?thCenturyClassicalComposers0
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
http://dbpedia.org/class/yago/20thCenturyClassicalComposers .
}} LIMIT 300
with the code provided here:
cf http://tech.groups.yahoo.com/group/jena-dev/message/48130
I get some results.
Now I try this query:
SELECT DISTINCT ?thCenturyClassicalComposers0 ?comment WHERE { SERVICE
http://api.talis.com/stores/bbc-backstage/services/sparql
{?thCenturyClassicalComposers0
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
http://dbpedia.org/class/yago/20thCenturyClassicalComposers .
} SERVICE http://dbpedia.org/sparql {?thCenturyClassicalComposers0
http://www.w3.org/2000/01/rdf-schema#comment ?comment} } LIMIT 300
I get no result.
But when checking data on each endpoint, I should get some results.
Is there something wrong in my SPARQL SERVICE syntax?
BTW, being able to limit/offset/orderBy and OPTIONALize each SERVICE
block would be uber nice ! ! ! Is it possible already?
Re: Basic federation in Jena
(same question as yesterday)
A few problems:
1/ Talis are turning off their online service so
http://api.talis.com/... will stop working sometime. If this is a
paid-for store, that wil be in several months; if hosted for free, it'll
happen in the next few days.
2/ The services have a 30s timeout - if that goes off, you get no
results from the SERVICE.
3/ DBpedia has
4/ You can use a subselect to restrict the remote query part:
SERVICE ... {
SELECT * {
...
} LIMIT 300
}
4/ Execution is bottom up:
The second block:
SERVICE http://dbpedia.org/sparql
{ ?thCenturyClassicalComposers0 rdf:comments ?comment }
may be executed repeatedly due to the execution strategty of ARQ
but when I try:
PREFIX rdfs:http://www.w3.org/2000/01/rdf-schema#
SELECT * { ?thCenturyClassicalComposers0 rdfs:comments ?comment }
at the DBpedia sparql endpoint I get:
Error HTTP/1.1 509 Bandwidth Limit Exceeded
Andy
On 31/07/12 08:40, Olivier Rossel wrote:
Hi all.
I would like to try Jena basic federation.
I tried this query:
SELECT DISTINCT ?thCenturyClassicalComposers0 WHERE { SERVICE
http://api.talis.com/stores/bbc-backstage/services/sparql {
?thCenturyClassicalComposers0
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
http://dbpedia.org/class/yago/20thCenturyClassicalComposers .
}} LIMIT 300
with the code provided here:
cf http://tech.groups.yahoo.com/group/jena-dev/message/48130
I get some results.
Now I try this query:
SELECT DISTINCT ?thCenturyClassicalComposers0 ?comment WHERE { SERVICE
http://api.talis.com/stores/bbc-backstage/services/sparql
{?thCenturyClassicalComposers0
http://www.w3.org/1999/02/22-rdf-syntax-ns#type
http://dbpedia.org/class/yago/20thCenturyClassicalComposers .
} SERVICE http://dbpedia.org/sparql {?thCenturyClassicalComposers0
http://www.w3.org/2000/01/rdf-schema#comment ?comment} } LIMIT 300
I get no result.
But when checking data on each endpoint, I should get some results.
Is there something wrong in my SPARQL SERVICE syntax?
BTW, being able to limit/offset/orderBy and OPTIONALize each SERVICE
block would be uber nice ! ! ! Is it possible already?
Re: Basic federation in Jena
Forcing the syntax to Syntax.syntaxARQ is mandatory because client-side federation is a ARQ-specific feature. Only in very old versions of ARQ - SERVICE is part of SPARQL 1.1 As far as I understand, SERVICE in SPARQL 1.1 is server-side federation. And you have no way to federate with local data. Whereas Syntax.syntaxARQ forces Jena-ARQ to be the federation query planner. And each SPARQL endpoint receives a part of the query with variables correctly pre-bound and no SERVICE keyword. Is that right?
