PROTÉGÉ SPARQL QUERY TAB: cannot query for ontology-specific classes

Question

I am using SPARQL Query tab in Protege 5 to query an OWL ontology I have been constructing. I succeded in many kinds of queries, but when I use some specific class of my ontology inside the very same queries (that are apparently well formed) they return no results. Following, two of the problematic queries - assuming "Event" as one of the concepts of the ontology (http://www.semanticweb.org/ontologies/2014/5/MyOnto#Event):

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX onto: <http://www.semanticweb.org/ontologies/2014/5/MyOnto#>

SELECT ?a  WHERE { ?a rdfs:subClassOf onto:Event } 

and, with the same prefixes

SELECT ?a  WHERE { ?a rdfs:range onto:Event } 

Both return no results. However, if I substitute "onto:Event" for, let's say, ?b, both return a long list of results - inclunding Event as a match for ?b.

Is it something I'm misusing or forgetting (although I've seen this pattern in several links on internet with people claiming to have got results) or is it a limitation of SPARQL or some issue of the Protege tab?

Answer 1

I had the same problem, whenever using an ontology specific class there were no results although there should have been. My ontology (pizza.owl) was loaded from a local file. I found that it is required to add the file name in the PREFIX.

PREFIX : <http://www.co-ode.org/ontologies/pizza/pizza.owl#>

After that I got the information that I expected.