Section: New Results

Avoiding shared clocks in networks of timed automata

Networks of timed automata (NTA) are widely used to model distributed real-time systems. Quite often in the literature, the automata are allowed to share clocks, i.e. the transitions of one automaton may be guarded by a condition on the value of clocks reset by another automaton. This is a problem when one considers implementing such model in a distributed architecture, since reading clocks a priori requires communications which are not explicitly described in the model.

In [58] , we focus on the following question: given an NTA $A_1\parallel A_2$ where $A_2$ reads some clocks reset by $A_1$, does there exist an NTA $A_1^{\text{'}}\parallel A_2^{\text{'}}$ without shared clocks with the same behavior as the initial NTA? For this, we allow the automata to exchange information during synchronizations only, in particular by copying the value of their neighbor's clocks.

We discuss a formalization of the problem and give a criterion using the notion of contextual timed transition system, which represents the behavior of $A_2$ when in parallel with $A_1$. Finally, we effectively build $A_1^{\text{'}}\parallel A_2^{\text{'}}$ when it exists.