Submitted to CONCUR ' 97 1 A Universal Reactive Machine

Turing showed the existence of a model universal for the set of Turing machines in the sense that given an encoding of any Turing machine as input the universal Turing machine simulates it. We introduce the concept of univer-sality for reactive systems and construct a ccs process universal in the sense that, given an encoding of any ccs process, it behaves like this process up to weak bisimulation. This construction has a rather non-constructive use of silent actions and we argue that this would be the case for any universal ccs process.