It is defined by the ITU-T (recommendation Z100) to provide a tool for unambiguous specification and description of the behaviour of telecommunications systems. The area of application also includes process control and real-time applications. SDL provides a Graphic Representation (SDL/GR) and a textual Phrase Representation (SDL/PR), which are equivalent representations of the same semantics. A system is specified as a set of interconnected abstract machines which are extensions of the Finite State Machine (FSM).
SDL is formally complete, so it can be used for code generation for either simulation or final targets.