PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX bio: <http://purl.org/vocab/bio/0.1/>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
SELECT ?name
WHERE { 
  ?person rdf:type foaf:Person ; foaf:name ?name .
  FILTER NOT EXISTS { 
	?person bio:event ?event .
  	?event rdf:type bio:Birth ; bio:date ?birthdate. }
}
