Memory-dependent abstractions of stochastic systems through the lens of transfer operators

TL;DR

This paper introduces memory-dependent abstractions for stochastic systems using transfer operators, enabling more accurate modeling of systems with memory effects and providing bounds on approximation errors.

Contribution

It presents a formalism for memory-dependent abstractions based on transfer operators and quantifies the approximation error with total variation bounds.

Findings

Memory-dependent abstractions capture non-Markovian dynamics.

Upper bounds on approximation errors are established.

The approach improves the fidelity of finite-state models of stochastic systems.

Abstract

With the increasing ubiquity of safety-critical autonomous systems operating in uncertain environments, there is a need for mathematical methods for formal verification of stochastic models. Towards formally verifying properties of stochastic systems, methods based on discrete, finite Markov approximations -- abstractions -- thereof have surged in recent years. These are found in contexts where: either a) one only has partial, discrete observations of the underlying continuous stochastic process, or b) the original system is too complex to analyze, so one partitions the continuous state-space of the original system to construct a handleable, finite-state model thereof. In both cases, the abstraction is an approximation of the discrete stochastic process that arises precisely from the discretization of the underlying continuous process. The fact that the abstraction is Markov and the discrete process is not (even though the original one is) leads to approximation errors. Towards accounting for non-Markovianity, we introduce memory-dependent abstractions for stochastic systems, capturing dynamics with memory effects. Our contribution is twofold. First, we provide a formalism for memory-dependent abstractions based on transfer operators. Second, we quantify the approximation error by upper bounding the total variation distance between the true continuous state distribution and its discrete approximation.