CTL-Like Fragments of a Temporal Logic of Robustness

The logic RoCTL* is an extension of the branching time temporal logic CTL* to represent robustness of systems to transient failures such as loss of data packets. New operators are introduced dealing with obligation (where no failures occur) and robustness (where at most one additional failure occurs). The only known decision procedures for the temporal logic of robustness RoCTL* are non-elementary. Here we propose two CTL-like restrictions of RoCTL*, Pair-RoCTL and State-RoCTL. We investigate whether it is possible to translate these fragments into CTL showing whilst this is not in general possible for Pair-RoCTL it is for State-RoCTL. We obtain a satisfiability preserving translation for State-RoCTL into CTL showing that the complexity of satisfiability of State-RoCTL is EXPTIME-complete. We also show that these fragments of RoCTL* are useful in specifying systems.