Speci cation and Re nement of a Real -

A number of timed-trace formalisms, where systems are modelled by time-varying functions, have been proposed for the formal development of real-time systems. In this paper, we illustrate one such approach via the speciication and reenement of the well-known Steam Boiler Control Problem. The case study illustrates the use of a timed-trace formalism to specify deadlines and other timing constraints, to reene system timing constraints into timing constraints of individual components, and to introduce internal timing constraints during system reenement.