Constraint-Oriented Style in LOTOS

The concept of a constraint-oriented specification style is presented in general terms and with respect to the ISO Formal Description Technique LOTOS (Language Of Temporal Ordering Specification ). The constraint-oriented style has proven very suitable for specifying the abstract, implementation-independent behaviour of systems in a modular fashion. The essential idea behind constraint-oriented specification is separation of concerns, which is facilitated by the behaviour combinators of LOTOS. The constraint-oriented style is illustrated by giving a highly-structured specification in LOTOS of the well-known AB (Alternating Bit) Protocol.