idea being you might simply want to log a message with no parameters.

  /**
   * Writes a message into the CASTOR logging system. Note that no exception
   * will ever be thrown in case of failure. Failures will actually be
   * silently ignored in order to not impact the processing.
   *
   * Note that this version of writeMsg() implicitly uses the current time as
   * the time stamp of the message.
   *
   * @param priority the priority of the message as defined by the syslog API.
   * @param msg the message.
   */
  virtual void writeMsg(
    const int priority,
    const std::string &msg) throw() = 0;