μ-Calculus pushdown module checking with imperfect state information

The model checking problem for open systems (module checking) has recently been the subject of extensive study. The problem was first studied by Kupferman, Vardi, and Wolper for finite-state systems and properties expressed in the branching time logics CTL and CTL*. Further study continued mainly in two directions: considering systems equipped with a pushdown store, and considering environments with imperfect information about the system. A recent paper combined the two directions and considered the CTL pushdown module checking problem in the imperfect information setting, i.e., in the case where the environment has only a partial view of the system control states and pushdown store content. It has been shown that this problem is undecidable when the environment has imperfect information about the pushdown store content, while it is decidable and 2EXPTIME-complete when the imperfect information only concerns control states. It was left open whether the latter remains decidable also for more expressive logics. In this paper, we answer this question in the affirmative, showing that the pushdown module checking problem with imperfect information about the control states is decidable and 2EXPTIME-complete for the propositional and the graded μ-calculus, and 3EXPTIME-complete for CTL*.