sclass TripleIndex extends VirtualNodeIndex {
  new SyncListMultiMap<S, TripleWeb> index;
  Map<GlobalID, TripleWeb> websByID = synchroHashMap();
  int size;

  int numWebs() {
    ret size;
  }
  
  L<WebNode> get(S query) {
    new L<WebNode> l;
    for (Web web : websFromTriples(index.get(query)))
      for (WebNode node : web_nodesAndRelations(web))
        if (web_hasText(node, query))
          l.add(node);
    ret l;
  }
  
  Web getWeb(GlobalID id) {
    ret webFromTriple(websByID.get(id));
  }
  
  void addWeb(Web web) {
    TripleWeb w = ai_webToTripleWeb(web);
    for (S s : lithashset(w.a, w.b, w.c)) { // only once
      index.put(s, w);
      ++size;
    }
    websByID.put(w.globalID, w);
  }
}