abstract sclass AbstractThoughtSpace {
  AbstractThoughtSpace parent;
  
  *() {}
  *(AbstractThoughtSpace *parent) {}
  
  // takes unshortened query
  abstract L<TripleRef<S>> get(S query);
  
  // existence of triple has already been checked
  abstract GlobalID postTriple(T3<S> t);
  
  abstract int size();
  
  public bool hasTriple(S a, S b, S c) {
    for (TripleRef<S> ref : shortestList3(get(a), get(b), get(c)))
      if (tripleEqic(ref.triple, a, b, c))
        true;
    false;
  }
}