sparqlowlprotegerdflibowlready

Protégé: Différent results between DL Query and SPARQL Query


Here is a small ontology called wildlife.owl, created by Protégé, in which I have classes animal, carnivore, herbivore, lion, giraffe, and individuals Léo (a lion), Gigi (a giraffe) and Giginou (also a giraffe). In the ontology I only declare that lion ⊏ carnivore ⊏ animal.

When I ask for the instances of animal in the DL Query tab of Protégé, I get, among others, Léo (which is a lion, hence a carnivore, hence an animal).

But when I write the following SPARQ Query:

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX me: <file:wildlife.owl#>
SELECT ?b
    WHERE { ?b rdf:type me:animal }

I don't get any instance. Same result when I replace me:animal by me:carnivore. Only when I replace it by me:lion I get the desired result Léo.

Why is DL Query doing the inference (allowing me to obtain Léo as instance of the animal class) and not SPARQL Query?

What can I do to get the same result in SPARQL Query?


Thanks to the answer by @UninformedUser I now know that I must use the Snap SPARQL Query and not the SPARQL Query.

My next question concerns Python: when I send the SPARQL Query using Owlready2 and RDFlib, again I get no result:

from owlready2 import *
from rdflib import *
onto = get_ontology("wildlife.owl").load()
sync_reasoner([onto])
graph = default_world.as_rdflib_graph()
print(list(graph.query_owlready("""
PREFIX rdf-syntax: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX me: <file:wildlife.owl#>
SELECT ?b WHERE {
?b rdf-syntax:type me:animal .
}""")))

How can I get this query use OWL Reasoner?


Solution

  • When calling the reasoner, Owlready does not retain trivia inferences, such as is-a transitivity (e.g. the fact that lion is an animal).

    For trivial inferences, you should rather use SPARQL, as in the example below. The ?any_animal variable contains all animal subclasses (including animal itself), thank to the SubclassOf* SPARQL syntax (the * indicates transitivity). Then, we take any instance of ?any_animal class.

        from owlready2 import *
        from rdflib import *
    
        onto = get_ontology("http://test.org/wildlife.owl")
    
        with onto:
            class animal(Thing): pass
            class carnivore(animal): pass
            class lion(carnivore): pass
    
            lion()
    
        default_world.graph.dump()
    
        graph = default_world.as_rdflib_graph()
    
        print(list(graph.query_owlready("""
        PREFIX rdf-syntax: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
        PREFIX me: <http://test.org/wildlife.owl#>
        SELECT ?b WHERE {
        ?any_animal <http://www.w3.org/2000/01/rdf-schema#subClassOf>* me:animal .
        ?b rdf-syntax:type ?any_animal .
        }""")))