“…Classical examples of this kind of 'simulation' are the implementation of sets by sequences or the implementation of stacks by arrays and pointers. Most of the implementation approaches in the literature fall into this category (for example, Goguen et al (1976), Guttag et al (1978), Ehrig et al (1978), Orejas (1981), Ehrich (1982), Ehrig et al (1982), Goguen and Meseguer (1982), Ehrig and Kreowski (1983), Ganzinger (1983), Kamin and Archer (1984), Orejas (1985), Bernot et al (1986), Broy et al (1986), Poigne (1984), Bernot (1989)). However, some others (for example, Sannella and Wirsing (1982), Sannella and Tarlecki (1988a), Schoett (1987), Hennicker (1989)) prefer to mix the two notions of refinement and simulation: SP' implements SP if the models of SP' behave like some models of SP.…”