Question: Which musician wrote the most books?
SPARQL query:
PREFIX onto: <http://dbpedia.org/ontology/>
PREFIX res: <http://dbpedia.org/resource/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT DISTINCT ?uri
WHERE {
        ?uri onto:occupation res:Musician .
        ?x onto:author ?uri .
        ?x rdf:type onto:Book .
}
ORDER BY DESC(COUNT(?x))
OFFSET 0 LIMIT 1