Before revision:  We restrict attention to physical systems that can be modeled as a time-inhomogeneous continuous-time Markov chain (CTMC) over a finite state space, which includes many of the systems considered in stochastic thermodynamics.
After revision:  We restrict attention to physical systems whose dynamics can be modeled as a time-inhomogeneous continuous-time Markov chain (CTMC) over a finite state space, which includes many of the systems considered in stochastic thermodynamics.