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