The use of formal methods in communications standards

Formal (i.e. mathematical) methods in computer science have been under development for the past 50 years, but the last 15 years has seen a great surge of interest in formal methods for specification. Communication systems have been a popular area for application of formal methods as they exhibit challenging technical features such as concurrency and distribution. The trend towards open systems, such as found in the ISO work on OSI) open systems interconnection), has provided a strong impetus for methods that allow interfaces and services to be specified precisely. In recognition of this, CCITT began work in 1976 on standardising SDL (specification and description language, Z.100) as a formal notation for telecommunications systems. Similarly ISO began work in 1980 on standardising Estelle (Extended finite state machine language, ISO 9074) and LOTOS (Language Of Temporal Ordering Specification, ISO 8807) for formal specification of open systems standards. All three languages reached a stable state in 1988, and have been widely applied to specifying communications standards