The main contributions of this thesis are presenting a ucm & sdl based method to model software requirement , discussing the process in detail and describing the requirements of a small real - time system ( automated teller machine , atm ) 本文主要贡献在于定义了一个基于ucm和sdl的软件需求描述模型,讨论了整个建模过程,并基于该方法描述了自动柜员机系统需求。