skos broader and narrow inverse not working

Question

I have setup GraphDB SE trial version and trying out inference functionality with OWL2-RL ruleset. I have built a simple SKOS knowledge with a single broader relationship. Some how, when I try to query for narrower relationship am not getting any results. Am I going wrong in the usage ?

Insertion:

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>
PREFIX owl: <http://www.w3.org/2002/07/owl#>

INSERT DATA {  
        ex:mammals rdf:type skos:Concept;
                   skos:prefLabel "mammals"@en;

        ex:animals rdf:type skos:Concept;
                   skos:prefLabel "animals"@en;
                   skos:broader ex:mammals .
}

Query:

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX skos: <http://www.w3.org/2004/02/skos/core#>

select * where {
    ?s skos:narrower ?o .
}

In the query result I don't see any response. Shouldn't it return below result - ex:mammals skos:narrower ex:animals

Answer 1

I just came across this question and the OP is correct: Although the official SKOS reference explicitly states that skos:broader and skos:narrower are inverse, the actual RDF implementation does not include this statement. However, properties skos:broaderTransitive and skos:narrowerTransitive are declared as inverse.

And, although not relevant to the original question, the implementation does not state properties skos:topConceptOf and skos:hasTopConcept as inverse either.