A graphical notation for representing Timed CSP (TCSP) specifications is presented. The notation, which integrates features from a number of existing specification languages, including Statecharts, is aimed at providing the means for more easily constructing and managing large TCSP specifications, with the intention of forming the basis for tools and a methodology for applying TCSP in the large. The graphical notation extends TCSP by allowing specifications to be both processes and arbitrary predicates, thus increasing the expressiveness and applicability of the notation. An extendible tool framework, designed for the graphical notation and to be integrated with other tools, is presented. We discuss the features of this framework, especially how it aims to support reasoning about TCSP specifications.

Debugging is one of the main uses of simulation. Localizing bugs or finding the reasons for unclear behavior involves going backwards in time, whereas simulation goes forward in time. Therefore, identifying causes with the aid of most existing simulation tools usually requires repeating the simulation several times, each time with reduced holes in the sieve. An alternative is simulation by deduction, a technique in which the steps in the dynamic behavior of the simulated model are deduced by a reasoning system. A simulation system that uses simulation by deduction can give direct answers to questions about the reasons for the simulation results. By recording the support for its deductions, such a system can answer "why" and "why not" questions about the scenario. Another benefit of simulation by deduction is that it enables symbolic simulation, that is, simulating a scenario given only a partial description of the environment and the simulated model. This allows verifying properties of...