2. Deterministically Timed Process Algebra

Concurrent and distributed systems are characterized not only by their functional behavior, but also by their quantitative features. A prominent role is played by timing aspects, which express the temporal execution of system activities. There are several different options for introducing time and time passing in system descriptions: durationless actions or durational actions, relative time or absolute time, global clock or local clocks. In this chapter, we present two timed process calculi arising from certain combinations of the options mentioned above, which share a deterministic representation of time and time passing suitable for real-time systems. Then, we show the impact of eager, lazy, and maximal progress interpretations of action execution on the expressiveness of timed descriptions and their bisimulation semantics. This is accomplished through a number of semantics-preserving mappings, which demonstrate how some of the different choices are not irreconcilable by providing a better understanding of benefits and drawbacks of the various time-related options.