I need to get the root element of a ontology

[Federico López]

I looking for a good quey that allows me to get the roots elements of a
Ontology. Also, I need to know wich one of these roots have children...


I have each ontology in a NAMED GRAPH....

This is what I using for it but the query is taking too much.

SELECT DISTINCT ?root ?label (COUNT(?child) AS ?nChild)
FROM  <http://ontologyURI>
WHERE
{
 ?root a ?class .
 ?class rdfs:subClassOf owl:Class .
 ?root rdfs:label ?label .
 OPTIONAL {
 ?root rdfs:subClassOf ?super .
 }
 OPTIONAL {
 ?child rdfs:subClassOf ?root .
 }
 FILTER (!bound(?super))
}
GROUP BY ?root ?label

Any idea?

Thanks...


-- 
*FEDERICO LÓPEZ GÓMEZ*
Estudiante Ingeniería de Sistemas
Universidad del Valle - Sede Tuluá