A Formal Specification of the Steam-Boiler Control Problem by Algebraic Specifications with Implicit State

In this section, we briefly present the formalism we use. This formalism aims at describing the state of a system and its dynamic behaviour in an algebraic framework [DG 94]. It was first introduced in a case study on a formal specification of the embedded safety part of an automatic subway pilot [DM 91], [Dau 92], [DGM 93], in order to cope with the large number of variables whose values made up the state of the system at a given time. A good analysis of the motivations of such formal approaches can be found in [EO 94]: the idea is to enrich algebraic specifications in order to make them more convenient for the description of dynamic behaviours. A comparison with similar works can be found in [DG 94] and [EO 94].