Specification and Description Language

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Specification and Description Language (SDL) is a specification language targeted at the unambiguous specification and description of the behaviour of reactive and distributed systems. It is defined by the ITU-T (Recommendation Z.100.) Originally focused on telecommunication systems, its current areas of application include process control and real-time applications in general.

SDL provides both a graphical Graphic Representation (SDL/GR) as well as a textual Phrase Representation (SDL/PR), which are both equivalent representations of the same underlying semantics. A system is specified as a set of interconnected abstract machines which are extensions of finite state machines (FSM).

SDL is formally complete, so it can be used for code generation for either simulation or final targets.

The first version of the specification language was released in 1976 using graphical syntax. The textual form was introduced later for machine processing. In 1988 SDL-88 was released containing object oriented concepts as inheritance, abstract generic types etc. The version released in 1992 had among other features an improved implementation support. SDL-2000 is the latest released version completely based on object-orientation. This version is accompanied by a SDL-UML-Profile.