Timing aspects of systems from a variety of computer science domains have been treated independently by different communities. Researchers interested in semantics, verification and performance analysis study models such as timed automata and timed Petri nets, the digital design community focusses on propagation and switching delays while designers of embedded controllers have to take account of the time taken by controllers to compute their responses after sampling the environment. Timing-related questions in these separate disciplines do have their particularities. However, there is a growing awareness that there are basic problems that are common to all of them. In particular, all these sub-disciplines treat systems whose behaviour depends upon combinations of logical and temporal constraints; namely, constraints on the temporal distances between occurrences of events.