Question: Was U.S. president Jackson involved in a war?
SPARQL:
PREFIX onto: <http://dbpedia.org/ontology/> PREFIX yago: <http://dbpedia.org/class/yago/> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> PREFIX dbpedia2: <http://dbpedia.org/property/> ASK WHERE { ?uri rdf:type yago:PresidentsOfTheUnitedStates . ?uri dbpedia2:name ?name . FILTER (regex(?name, 'Jackson')) . OPTIONAL {?uri onto:battle ?battle .} FILTER BOUND(?battle). }