Compositional Visible Bisimulation Abstraction Applied to Opacity Verification

Paper in proceeding, 2018

In this paper, an alternative equivalence based definition of bisimulation is proposed, called
visible bisimulation equivalence. It includes both state and transition labels and therefore unifies
stuttering and branching bisimulation. Furthermore, it is equivalent to a temporal logic called ECTL*,
where CTL* is extended with events. The presented bisimulation abstraction is applied to a set of
synchronized submodels, where local events are identified incrementally and abstracted after each
synchronization. Since the bisimulation reduction is applied after each synchronization, a significant
part of the state space explosion in ordinary synchronization is avoided. This compositional abstraction
is used for opacity verification, where it is shown that local observers can be generated before they are
synchronized, a key factor to be able to apply compositional opacity verification. The efficiency of this
method is illustrated on a modular opacity problem with mutual exclusion of moving agents.