Omega-Regular Reward Machines

Reinforcement learning (RL) is a powerful approach for training agents to perform tasks, but designing an appropriate reward mechanism is critical to its success. However, in many cases, the complexity of the learning objectives goes beyond the capabilities of the Markovian assumption, necessitating a more sophisticated reward mechanism. Reward machines and ω-regular languages are two formalisms used to express non-Markovian rewards for quantitative and qualitative objectives, respectively. This paper introduces ω-regular reward machines, which integrate reward machines with ω-regular languages to enable an expressive and effective reward mechanism for RL. We present a model-free RL algorithm to compute ϵ-optimal strategies against ω-regular reward machines and evaluate the effectiveness of the proposed algorithm through experiments.