SDL (Specification and Description Language) is a program design and implementation language that is used to build real-time event-driven systems that involve parallel processing . Some advantages of SDL, according to its proponents, include mathematical rigor, clarity, consistency, portability, scalability, and the ability to interface with other languages. It is described as a graphical language that eliminates ambiguity.
The earliest applications of SDL, which has evolved from ideas first developed in 1976, were in telecommunications, particularly in the aerospace industry. More recent applications include medical devices, railway control systems, automotive systems, satellite networks, remote control, remote monitoring, telepresence, and robotic systems.