SDL: the standard for engineering telecommunications software

The paper gives the standardisation background, an overview and usage of information on CCITT SDL which is the formal description technique standardised by CCITT for the specification of the behaviour of real time (telecommunications) systems. Although it has been standardised since 1976 and is widely used in the telecommunications industry and standards work, it has not been widely used elsewhere. Despite its age, SDL is evolving in a controlled way to meet present requirements. The standardisation work and available support is described. Key features of the language are described in an overview. The current industrial usage is briefly reported, and is supported by references.<>