A concurrent system of synchronous communicating agents is assembled from simpler sequential agents by parallel composition and hiding. For example, hide a 1 ; : : :a l in (p 1 kp 2 : : :kp n ) describes the system of communicating agents p 1 ; : : :p n in which the communication events a 1 ; : : :a l are hidden. Consider descriptions of two systems p and q of synchronously communicating nite state agents. Assume that one wants to check whether p q for one of the commonly used equivalence . We show that this question is PSPACE hard for all equivalences that lie between strong bisimulation and trace equivalences. For some equivalences exponential lower and upper bounds are proven. We also show that this problem is NP hard and co-NP hard even for a class of very simple nite agents. 3
It was also conjectured in REF that the problem is EXPTIME-hard for any relation between bisimilarity and trace equivalence.
Complexity of Equivalence Problems for Concurrent Systems of Finite Agents
Informs Journal on Computing
Computer Science Mathematics