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).
2. Specification and Description Language. ITU-T. Specification language with both graphical and character-based syntaxes for defining interacting extended finite state machines. Used to specify discrete interactive systems such as industrial process control, traffic control, and telecommunication systems. Proc Plenary Assembly, Melbourne 14-1988-11-25, Fasc X.1, CCITT. "Telecommunications Systems Engineering Using SDL", R. Saracco et al, N-H 1989. Available from Verilog, MD. (See XDL).