I need to return individuals for my query:
SELECT ?subject ?class
WHERE { ?subject rdfs:subClassOf ?class.
?class rdfs:comment "linear"#en}
But it works only with subclasses. Should I replace rdfs:subClassOf on different operator?
Your query specifically asks for ?subjects that are subclasses of ?class (where ?class has the rdfs:comment "linear"#en). To retrieve instances of type ?class, you'd use
?subject rdf:type ?class
or, since SPARQL allows abbreviating rdf:type by a,
?subject a ?class
If you can't share details about the body of data, you are querying, you might want to get an idea yourself by checking
SELECT ?s ?p ?subject ?class
WHERE
{ ?s ?p ?class .
?subject rdfs:subClassOf ?class .
?class rdfs:comment "linear"#en .
} ORDER BY ?s ?p ?subject ?class
and/or
SELECT ?subject ?class ?p ?o
WHERE
{ ?subject ?p ?o .
?subject rdfs:subClassOf ?class .
?class rdfs:comment "linear"#en .
} ORDER BY ?subject ?class ?p ?o
from where you can expand in the same manner until you get a handle.
Related
I have an RDF graph G with several classes assuming for simplicity (Person and Parrot).
The class Person is connected to the class Parrot by the property hasAnimal, e.g.:
#PREFIX : <http://example.org/>
:Hugo rdf:type :Person .
:Hugo rdfs:label "Hugo" .
:Hugo :hasAnimal :Birdy.
:Birdy rdf:type :Parrot .
:Birdy rdfs:label :"Birdy" .
:LonleyBrido rdf:type :Parrot .
What is wanted is a subgraph of G that contains all the triples from Person and Parrot that are directly connected with each other, starting from Person. The initial Person does not matter to me, the important part is that only connected triples are extracted i.e. that only persons that do have a parrot or don't get outputted. What I have already tried is the following:
construct {
?person ?p ?o .
?parrot ?p2 ?o2 .
} where {
?person rdf:type :Person .
?person ?p ?o .
?person :hasAnimal ?parrot .
?parrot rdf:type :Parrot .
?parrot ?p2 ?o2 .
}
So the expected output would be:
:Hugo rdf:type :Person .
:Hugo rdfs:label "Hugo" .
:Hugo :hasAnimal :Birdy.
:Birdy rdf:type :Parrot .
:Birdy rdfs:label :"Birdy" .
I am executing this query on a rdflib graph.
Does anyone have a solution to this problem?
The solution is already described above:
import rdflib
from rdflib.namespace import RDF, RDFS
query = """
construct {
?person ?p ?o .
?parrot ?p2 ?o2 .
} where {
?person rdf:type :Person .
?person ?p ?o .
?person :hasAnimal ?parrot .
?parrot rdf:type :Parrot .
?parrot ?p2 ?o2 .
}
"""
g = rdflib.Graph()
g.parse("example.ttl", format="ttl")
g.bind("rdf", RDF)
g.bind("rdfs", RDFS)
EX= rdflib.Namespace("http://example.org/")
g.bind("example", EX)
result = g.query(query)
I have the following SPARQL query
SELECT DISTINCT ?p ?class ?type
WHERE {
?resource ?p ?target .
?p rdfs:range ?class .
?class rdf:type ?type .
}
I get results only for the object properties.
If ?class = xsd:float, then rdf:type = rdfs:Datatype, right?
Why I do not receive also results for the type of data properties?
Assuming the triples are following:
#prefix : <http://example/> .
#prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
#prefix foaf: <http://xmlns.com/foaf/0.1/> .
:alice rdf:type foaf:Person .
:alice foaf:name "Alice" .
:bob rdf:type foaf:Person .
and then we perform 3 queries based on SPARQL 1.1:
Q1:
SELECT ?s
WHERE
{
?s ?p ?o .
FILTER NOT EXISTS { ?s foaf:name ?y }
}
Q2:
SELECT ?s
WHERE
{
?s ?p ?o .
FILTER NOT EXISTS { ?x foaf:name ?y }
}
Q3:
SELECT ?s
WHERE
{
?s ?p ?o .
FILTER NOT EXISTS { ?x foaf:mailbox ?y }
}
These three queries return three different solutions. Could anyone help me figure out why Q2 evaluates to no query solution in contrast to Q1 and Q3? Many thanks in advance :)
Q2 returns no solution because in your data, there exists a statement that matches ?x foaf:name ?y: ?x = :alice and ?y = "Alice". You've put no further constraints on either ?x or ?y. So no matter what the other variables in your query (?s, ?p and ?o) are bound to, the NOT EXISTS condition will always fail and therefore the query returns no result.
I uploaded a set of RDF triples onto a local Virtuoso endpoint.
Of all these triples, I would like to extract only those whose subjects have at least the predicates http://www.w3.org/2000/01/rdf-schema#label and http://www.w3.org/2000/01/rdf-schema#comment.
For example, from these triples:
<http://dbpedia.org/resource/AccessibleComputing> <http://www.w3.org/2000/01/rdf-schema#label> "AccessibleComputing"#en .
<http://dbpedia.org/resource/AfghanistanGeography> <http://www.w3.org/2000/01/rdf-schema#label> "AfghanistanGeography"#en .
<http://dbpedia.org/resource/AfghanistanGeography> <http://www.w3.org/2000/01/rdf-schema#comment> " ... " .
<http://dbpedia.org/resource/Austroasiatic_languages> <http://www.w3.org/2000/01/rdf-schema#comment> " ... " .
<http://dbpedia.org/resource/AccessibleComputing> <http://dbpedia.org/ontology/wikiPageWikiLink> <http://dbpedia.org/resource/Computer_accessibility> .
<http://dbpedia.org/resource/AfghanistanGeography> <http://dbpedia.org/ontology/wikiPageWikiLink> <http://dbpedia.org/resource/Afghanistan_Geography> .
I would like to get:
<http://dbpedia.org/resource/AfghanistanGeography> <http://www.w3.org/2000/01/rdf-schema#label> "AfghanistanGeography"#en .
<http://dbpedia.org/resource/AfghanistanGeography> <http://www.w3.org/2000/01/rdf-schema#comment> " ... " .
<http://dbpedia.org/resource/AfghanistanGeography> <http://dbpedia.org/ontology/wikiPageWikiLink> <http://dbpedia.org/resource/Afghanistan_Geography> .
Is it possible to do this with one (or more) SPARQL query?
Thank you for helping
This can be done with a CONSTRUCT WHERE query:
CONSTRUCT WHERE {
?s rdfs:label ?label.
?s rdfs:comment ?comment.
?s ?p ?o
}
This is a simplified form of CONSTRUCT that can be used when the CONSTRUCT {} part and the WHERE {} part are identical.
One way is to use DESCRIBE, e.g.:
DESCRIBE ?s
WHERE {
?s rdfs:label ?label .
?s rdfs:comment ?comment .
}
or alternatively with CONSTRUCT :
CONSTRUCT { ?subject ?predicate ?object}
WHERE {
?subject ?predicate ?object .
FILTER EXISTS {
?subject rdfs:label ?label .
?subject rdfs:comment ?comment .
}
}
In a query like this, how can I avoid ?p being bound to rdf:type?
select ?p ?c where {
<http://dbpedia.org/resource/Istance_1> ?p ?c.
<http://dbpedia.org/resource/Istance_2> ?p ?c.
}
Add a filter to your query:
select ?p ?c where {
<http://dbpedia.org/resource/Istance_1> ?p ?c.
<http://dbpedia.org/resource/Istance_2> ?p ?c.
filter( ?p != rdf:type )
}
It's typical to use the prefix dbpedia: for http://dbpedia.org/resource/, and I expect that Istance is suppose to be Instance, so with a bit of cleanup, you'll have
prefix dbpedia: <http://dbpedia.org/resource>
select ?p ?c where {
dbpedia:Instance_1 ?p ?c .
dbpedia:Instance_2 ?p ?c .
filter( ?p != rdf:type )
}
If you're copying and pasting into the public DBpedia SPARQL endpoint, you won't need to define that prefix because it, and bunch of others are predefined, but if you'll calling it some other fashion, you will need to.