static L<S> webs_readTripleFile(InputStream in) {
  try {
    Iterator<S> it = linesFromInputStream(in);
    L<S> names = (L) unstructure(it.next());
    new L<Web> webs;
    while (it.hasNext()) {
      S s = it.next();
      pcall {
        L<S> l = splitAtSpace(s);
        if (l(l) == 3)
          webs.add(webFromTriple(
            names.get(parseInt(first(l))), 
            names.get(parseInt(second(l))),
            names.get(parseInt(last(l)))));
      }
    }
  } finally {
    in.close();
  }
  ret webs;
}