String prefLabel = id.replace('_', ' ');
URI conceptUri = URI.create(namespace + id);
SKOSConcept concept = dataFactory.getSKOSConcept(conceptUri);
concepts.add(concept);
// skos:narrower
objectRelationAssertions.add(dataFactory.getSKOSObjectRelationAssertion(topConcept, dataFactory.getSKOSNarrowerProperty(), concept));