This Recommendation defines SDL (Specification and Description Language) intended for unambiguous specification and description of telecommunication systems. The scope of SDL is elaborated in clause 1. This Recommendation is a reference manual for the language.


SDL has concepts for behaviour, data description and (particularly for larger systems) structuring. The basis of behaviour description is extended finite state machines communicating by messages. Data description is based on data types for values and objects. The basis for structuring is hierarchical decomposition and type hierarchies. These foundations of SDL are elaborated in the respective main clauses of this Recommendation. A distinctive feature of SDL is the graphical representation.


SDL is applicable within standard bodies and industry. The main applications areas for which SDL has been designed are stated in 1.2, but SDL is generally suitable for describing reactive systems. The range of application is from requirement description to implementation.