abstract sclass AbstractThoughtSpace {
  AbstractThoughtSpace parent;
  
  // takes unshortened query
  abstract L<WebNode> get(S query);
  
  // existence of triple has already been checked
  abstract S postTriple(T3<S> t);
  
  abstract int size();
  
  public bool hasTriple(S a, S b, S c) {
    L<Web> webs = ai_withoutInvalidWebs(nodesToWebs(shortestList3(
      get(a),
      get(b),
      get(c))));
    ret webs_search_noVar_bool(webFromTriples(a, b, c), webs);
  }
}