I'm new to SPARQL hope someone could help me.
The problem is that if I run the following query on dbpedia sparql:
SELECT DISTINCT ?class WHERE {
?s a ?class.
}
it returns:
result query
I would like to remove the results that has this two prefix: "http://www.w3.org/2002/07/owl" and "http://www.w3.org/2000/01/rdf-schema", now the query is:
SELECT DISTINCT ?class WHERE {
?s a ?class.
FILTER ( !strstarts(str(?class), "http://www.w3.org/2002/07/owl") ).
FILTER ( !strstarts(str(?class), "http://www.w3.org/2000/01/rdf-schema") ).}
but it returns only one result:
http://www.w3.org/1999/02/22-rdf-syntax-ns#Property
If I execute the same query on istat sparql these queries work fine.
So the question is, why on dbpedia my queries does not work as expected?
Thanks
Related
So when I run this SPARQL query on the DBpedia SNORQL interface it works --
select *
{ ?s rdf:type <http://dbpedia.org/class/yago/Company108058098> }
limit 10
But a similar query doesn't work --
select *
{ ?s dct:subject <http://dbpedia.org/page/NEC> }
limit 5
Can anyone tell me where am I doing it wrong ?
I'm doing a small exercise on sparql. Using Dbpedia Endpoint, I need to count number of triples.
This is my query
// Get the number of triples //
SELECT (COUNT(*) as ?Triples) WHERE { ?s ?p ?o}
-------------------------------------------------------
OUTPUT:
( ?Triples = 1625382483 )
Just wondering are the query and the result right?
Is this how you get the number of triples?
You can sanity check many things by executing queries directly on a SPARQL endpoint, rather than going through Jena or other intermediary clients. For instance, your query on the DBpedia form, and its results, which shows all triples in that triplestore (currently 1,625,382,483).
If you want the count of triples only within the DBpedia named graph (currently 438,336,517), you'll need to specify that, either in the SPARQL form Default Data Set Name (Graph IRI), or directly in the query, as in --
SELECT (COUNT(*) as ?Triples)
WHERE
{ GRAPH <http://dbpedia.org>
{ ?s ?p ?o }
}
-- or --
SELECT (COUNT(*) as ?Triples)
FROM <http://dbpedia.org>
WHERE { ?s ?p ?o }
I need to find all triples on DBpedia where http://dbpedia.org/resource/Benin is a subject or object. This query gives me the output that I want in a format that works the best for me (just three variables and no blank spaces):
PREFIX : <http://dbpedia.org/resource/>
SELECT * WHERE {
?s ?p ?o
FILTER (?s=:Benin OR ?o=:Benin)
}
I get similar results if I have this query:
PREFIX : <http://dbpedia.org/resource/>
SELECT * WHERE {
{:Benin ?p ?o}
UNION
{?s ?p :Benin}
}
However, the formatting of the latter is off. It first gives me p and o output leaving s blank and then s and p leaving o blank. Also, the first query takes more time to execute. I will be grateful for an explanation of the mechanics of how the two queries work and why there is a difference in the output.
However, the formatting of the latter is off
That's because both queries have different result sets together with SELECT *. The union joins the tuples, but since some tuples are missing parts, you get skewed output.
You can resolve the problem by explicitly listing and selecting the variables:
PREFIX : <http://dbpedia.org/resource/>
SELECT ?s ?p ?o WHERE {
{
?s ?p ?o
FILTER (?s=:Benin)
}
UNION
{
?s ?p ?o .
FILTER (?o=:Benin)
}
}
Note that this is still much faster on dbpedia than the OR filter.
The union will return duplicates when a tuple matches both filter expressions (i.e. :Benin ?p :Benin).
SELECT DISTINCT would remedy that at additional cost and since it looks like the problem is non-existent, I omitted it for improved performance.
Also, the first query takes more time to execute.
That's hard to say without the result of an EXPLAIN(), but my first guess would be that the equality filter is using the index, while the OR filter is using a full table scan. Virtuoso does not seem to generate good query plans for nested filters.
Try this --
PREFIX : <http://dbpedia.org/resource/>
DESCRIBE :Benin
-- or just --
DESCRIBE <http://dbpedia.org/resource/Benin>
You can get the output in various other serializations, including N-triples.
i have to use ROWLKit
http://www.dis.uniroma1.it/quonto/?q=node/30
(1) can anybody suggest two sparql queries for the Pizza.owl ?
(2) is this query valid ?
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX pizza: <http://www.co-ode.org/ontologies/pizza/pizza.owl#>
SELECT *
WHERE { ?p rdf:type pizza:Pizza;
pizza:hasTopping ?t.
?t rdf:type pizza:TomatoTopping }
(3) if it is a valid query then: is the response an empty result?
SELECT DISTINCT *
WHERE {
?NombrePizza ?Relacion pizza:MushroomTopping .
?Relacion owl:inverseOf pizza:isToppingOf .
OPTIONAL {
?NombrePizza2 ?Relacion2 pizza:HamTopping .
?Relacion2 owl:inverseOf pizza:isToppingOf .
}
FILTER(?NombrePizza2 = ?NombrePizza)
}
(1) can anybody suggest two sparql queries for the Pizza.owl ?
Here are two examples:
SELECT * WHERE { ?s ?p ?o }
and:
SELECT ?class WHERE { ?class a owl:Class }
(2) is this query valid ?
Yes.
(3) if it is a valid query then: is the response an empty result?
I assume that you mean "if I query the RDF document that serialises the pizza ontology, is the response an empty result?". The answer is yes.
(2) appears to be a valid query
I don't understand part (3) of your question. (2) cannot be compared to a boolean since it returns a Result Set, if you want a boolean result then you need to use an ASK query. If an ASK query returns true then it means that there are solutions to the query in the data you are querying so it would not be an empty result.
I want to select a triple using SPARQL. To do it, i'm using following query:
SELECT count (*)
WHERE {?s ?p ?o}
FILTER (?s=http://kjkhlsa.net && ?p=http://lkasdjlkjas.com && ?o=Test)
As answer i get fully wrong triple :( subject ist not equal to "http://kjkhlsa.net", predicate is not equal to "http://lkasdjlkjas.com" and object ist also not equal to "Test". Can someone explain me, what I'm doing wrong :(
edit1:
I have put the query into php file:
$inst_query = 'SELECT * { <http://kjkhlsa.net> <http://lkasdjlkjas.com> "Test"}';
echo $inst_query;
The answer from the echo was "SELECT * { "Test"}". Then i tried it with WHERE:
$inst_query = 'SELECT * WHERE { <http://kjkhlsa.net> <http://lkasdjlkjas.com> "Test"}';
echo $inst_query;
Here was the answer "SELECT * WHERE { "Test"}"...so, i'm missing the URIs, but this seems for me as php issue and not sparql problem.
edit2:
I've put the query into SPARQL Query editor and i get the response "no result"....but I'm sure, that i have this triple.
In its current form the question is not very clear (see my comment above).
Since you are essentially trying to get triples matching a pattern, it is more efficient to use a graph pattern instead of FILTER. Many SPARQL implementations first match candidate triples by graph patterns and only then apply the FILTER expression. In essence, with a ?s ?p ?o graph pattern, you're doing a linear scan over all your triples.
So, here's something that should work, using graph patterns instead of FILTER.
SELECT * { <http://kjkhlsa.net> <http://lkasdjlkjas.com> "Test" }
Notes: I didn't include COUNT(*) which is not standard SPARQL. <> around URIs. "" around literal.
Try to use this :
SELECT count (*) as ?count
WHERE {
?s ?p ?o
FILTER (?s=<http://kjkhlsa.net> && ?p=<http://lkasdjlkjas.com> && ?o=Test)
}
The following query uses the count function to count the number of distinct URI(s) returned to the ?s variable.
SELECT ?s (COUNT (DISTINCT ?s) as ?count)
WHERE {?s ?p ?o}
FILTER (?o="Test")