concept Str extends DefiniteThing {
  S name;
  new L<S> otherNames;
  
  *() {}
  *(S *name) {}
  
  public S toString() { ret name; }
}

static Str concept(S name) {
  for (Str s : list(Str.class))
    if (eqic(s.name, name) || containsIgnoreCase(s.otherNames, name))
      ret s;
  ret new Str(name);
}

static void mergeStrs(Str a, Str b) {
  if (a == b) ret;
  if (nempty(b.backRefs)) {
    Str t = a;
    a = b;
    b = t;
  }
  a.otherNames.add(b.name);
  a.otherNames.addAll(b.otherNames);
  if (nempty(b.backRefs))
    print("Warning: Deleting concept with back references - " + b.name);
  b.delete();
}