State-transition systems model machines, programs, and speci?cations 20, 23,284,329], butalsothegrowthanddeclineofantpopulations, ?nancial markets, diseases and crystals 22, 35, 178, 209, 279]. In the last decade, thegrowinguseofdigitalcontrollersinvariousenvironmentshasentailed theconvergenceofcontroltheoryandreal-timesystemstowardhybrids- tems 16] by combining both discrete-event facets of reality with Nature s continuous-time aspects. The computing scientist and the mathematician have re-discovered each other. Indeed, in the late sixties, the programming language Simula, father of...