摘要:Given two labelled Markov decision processes (MDPs), the trace-refinementproblem asks whether for all strategies of the first MDP there exists astrategy of the second MDP such that the induced labelled Markov chains aretrace-equivalent. We show that this problem is decidable in polynomial time ifthe second MDP is a Markov chain. The algorithm is based on new results on aparticular notion of bisimulation between distributions over the states.However, we show that the general trace-refinement problem is undecidable, evenif the first MDP is a Markov chain. Decidability of those problems was statedas open in 2008. We further study the decidability and complexity of thetrace-refinement problem provided that the strategies are restricted to bememoryless.