// not synchronized
sclass WebThoughtSpace extends OptionalConcept {
  S globalID;
  new Webs webs;
  new L<Web> openQuestions;
  
  transient Map<S, Web> websByID;
  transient MultiMap<S, WebNode> index;

  class Webs extends NotifyingList<Web> {
    *() { super(new L); }
    *(L<Web> l) { super(l); }
    
    public synchronized bool add(Web web) {
      synchronized(this) {
        if (!list.add(e)) false;
      }
      if (index != null)
        ai_addWebToIndex(index, web);
      if (websByID != null)
        websByID.put(web.globalID, web);
    }
    
    void change() {
      index = null;
      websByID = null;
    }
    
    public synchronized L<Web> subList(int i, int j) {
      ret new Webs(list.subList(i, j));
    }
  }

  *() {}
  *(Web... webs) {
    addAll(this.webs, webs);
  }
  
  void addWeb(Web web) { webs.add(web); }
  
  WebNode indexedNode(S query) { ret first(indexedNodes(query)); }
  L<WebNode> indexedNodes(S query) {
    if (index == null)
      index = ai_indexWebs(webs);
    ret index.get(query);
  }
}