@Override
 protected void initOptions() {
   super.initOptions();
   options.addOption(
       null,
       lowerPrefixOption,
       true,
       "Prefix for lower reachability traces (default: name of the 'links' trace)");
   options.addOption(
       null,
       upperPrefixOption,
       true,
       "Prefix for upper reachability traces (default: prefix+'_upper')");
 }
 @Override
 protected void parseArgs(CommandLine cli, String[] args)
     throws ParseException, ArrayIndexOutOfBoundsException, HelpException {
   super.parseArgs(cli, args);
   long tau = Long.parseLong(args[1]);
   long delay = Long.parseLong(args[2]);
   String lower_prefix =
       cli.hasOption(lowerPrefixOption)
           ? cli.getOptionValue(lowerPrefixOption)
           : LinkTrace.defaultName;
   lower_name = ReachabilityTrace.defaultName(lower_prefix, tau, delay);
   String upper_prefix =
       cli.hasOption(upperPrefixOption)
           ? cli.getOptionValue(upperPrefixOption)
           : lower_prefix + "_upper";
   upper_name = ReachabilityTrace.defaultName(upper_prefix, tau, delay);
 }