orts") ?>

  <P>
    A more radical way to prevent write access is to prevent the system
    components that enable it from being imported <em>at all</em>.
    A rule for the <a href="policy.html#capabilities><TT>"componentLoad"</TT></a>
    capability can be set for this purpose:
  </P>

  <PRE class=code>
    fun noIOCom url =
        case Url.toString url of
        | "x-alice:/lib/system/TextIO"
        | "x-alice:/lib/system/BinIO" => REJECT
        | _ => PASS

    do Policy.Url.rule("componentLoad", 