code: package it.unibz.inf.ontop.iq.visit.impl;
  
  import it.unibz.inf.ontop.iq.node.ExtensionalDataNode;
  import it.unibz.inf.ontop.iq.node.IntensionalDataNode;
  
  import java.util.stream.Stream;
  
  public class RelationExtractor extends AbstractPredicateExtractor<ExtensionalDataNode> {
  
      public RelationExtractor() {
      }
  
      @Override
      public Stream<ExtensionalDataNode> visitIntensionalData(IntensionalDataNode dataNode) {
          return Stream.empty();
      }
  
      @Override
      public Stream<ExtensionalDataNode> visitExtensionalData(ExtensionalDataNode dataNode) {
          return Stream.of(dataNode);
      }
  }
  