Specification and Description Language. SDL is a specification language applied for modeling behavior of reactive and distributed systems, whose behavior is defined by real-time events.
Its main features are possibility to use as a spectrum language from requirement to implementation; suitability for real-time systems; graphical presentation; models based on communication processes; object-oriented description of components. It was created as a language for telecommunication systems, and now it is widely used in different spheres from aircraft and train control to medical and packaging systems.