I agree with the previous post. Add it as an Actor. And actor doesnt need to be a person, its anything outside the interacts with the systems. Just like this external system is interacting with ur system. An actor can even be time.
PLEASE WATCH THIS VIDEO: <a href="http://www.glumbert.com/media/dolphin" target="_blank" rel="nofollow">http://www.glumbert.com/media/dolphin</a><br /> <br /><-- that video is no joke. Spread the word... this cant go on!!!<br /> <br />SCJP 1.4, SCBCD 1.3, SCWCD 1.4, SCMAD 1.0