static Set<GlobalID> ai_invalidWebIDsFromDB() {
  new HashSet<GlobalID> ids;
  new Matches m;
  for (TripleWeb w : ai_triples("$X", "is", "invalid"))
    if (swic_trim(w.a, "Web ", m) && isGlobalID($1))
      ids.add(asGlobalID($1));
  ret ids;
}