code: boolean rule6(final IFactory factory, final Inclusion[] gcis) {
          boolean result = false;
  
          if (rhs instanceof Existential) {
              Existential existential = (Existential) rhs;
              final AbstractConcept cHat = existential.getConcept();
              if (!(cHat instanceof Concept)) {
                  result = true;
                  Concept a = getA(factory, cHat);
                  gcis[0] = new GCI(lhs,
                          new Existential(existential.getRole(), a));
                  gcis[1] = new GCI(a, cHat);
              }
          }
  
          return result;
      }
docs: B &#8849; &#8707;r.C' &rarr; {B &#8849; &#8707;r.A, A &#8849; C'}
  
  @param gcis
  @return