What is the {sovereign state} for {time period} of {Roman Empire}
Who is the {imperial state} for {time period} of {Roman Empire}
Who is the {sovereign state} for {time period} of {Roman Empire}
SELECT DISTINCT ?c WHERE { resource:Roman_Empire property:time_period ?c . ?c rdf:type ontology:sovereign_state }
select distinct ?obj where { ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> <http://wikidata.dbpedia.org/resource/Q2277> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P2348> . ?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> ?obj . ?obj <http://www.wikidata.org/entity/P31> <http://wikidata.dbpedia.org/resource/Q3624078> } 
 select distinct ?obj where { wd:Q2277 wdt:P2348 ?obj . ?obj wdt:P31 wd:Q3624078 } 