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