Corese FAQ

Olivier Corby, INRIA, June 2008.
See also: Corese

SPARQL query does not retrieve an instance given its URI ? an instance of a Class ?

Check the xml:base of the RDF document and/or the namespace of the class in the RDF and in the RDFS documents. Check the prefix declaration in the query. Namespaces must be rigorously the same in the documents and in the query.

How can I retrieve all the subclasses of a class ?

<owl:TransitiveProperty rdf:about='&rdfs;subClassOf' />

prefix my: <http://www.example.org/ontology#>
select ?sub where {
  ?sub rdfs:subClassOf my:Class
}

Then how can I retrieve the direct subclasses of a class ?

prefix my: <http://www.example.org/ontology#>
select ?sub where {
  ?sub direct::rdfs:subClassOf my:Class
}

How can I retrieve all resources linked to a given resource ?

select ?y where {
  <uri> ?p ?y
}

How can I retrieve all resources linked to a given resource with properties from a given ontology ?

prefix my: <http://www.example.org/ontology#>
select ?y where {
  <uri> ?p ?y
  filter(?p ^ my:)
}

How can I check that a resource is not linked to another resource, by any property ?

prefix my: <http://www.example.org/ontology#>
select ?x where {
  ?x ?p ?y 
  optional {
    ?x ?q <uri>
  }
  filter(! bound(?q))
}

How can I model and query an n-ary relation ?

<rdf:Description rdf:about='#myCar'>
  <my:speed rdf:parseType='Resource'>
     <rdf:value>100</rdf:value>
     <my:unit>km/h</my:unit>
  </my:speed>
</rdf:Description>

prefix my: <http://www.example.org/ontology#>
select ?speed ?unit where {
  ?car my:speed [ rdf:value ?speed ; my:unit ?unit ]
}