PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX aa: <https://moex.gitlabpages.inria.fr/alignapi/tutorial/tutorial4/ontology1.owl#>

SELECT ?fn ?ln ?t ?s
WHERE {
      ?student rdf:type aa:Estudiante .
      ?student aa:firstname  ?fn .
      ?student aa:lastname  ?ln .
OPTIONAL   {   ?student aa:affiliation ?t . }
OPTIONAL   {   ?student aa:supervisor ?s . }
}