sclass AI_SubSpace implements AI_PostHandler, AI_CacheChecker {
  int limit;
  new MultiMap<S, WebNode> index;
  new HashMap<S, Web> websByID;
  new L<Web> webs;
  
  *() {}
  *(int *limit) {}
  
  // existence of triple has already been checked
  public S postTriple(T3<S> t) {
    if (limitReached()) fail("Subspace limit reached");
    Web web = webFromTriple(t);
    websByID.put(web.globalID, web);
    webs.add(web);
    for (WebNode node : web_nodesAndRelations(web))
      for (S text : asSet(node.texts())) 
        index.put(ai_shortenForIndex(text), node);
    ret web.globalID;
  }
  
  public bool hasTriple(S a, S b, S c) {
    L<Web> webs = ai_withoutInvalidWebs(nodesToWebs(shortestList3(
      index.get(a),
      index.get(b),
      index.get(c))));
    ret webs_search_noVar_bool(webFromTriples(a, b, c), webs);
  }
  
  bool limitReached() {
    ret limit > 0 && l(websByID) >= limit;
  }
  
  L<WebNode> indexedNodes_rawLookup(s) {
    ret index.get(ai_shortenForIndex(s));
  }
}