  Formally verifying Deep Reinforcement Learning (DRL) systems is a challenging
task due to the dynamic continuity of system behaviors and the black-box
feature of embedded neural networks. In this paper, we propose a novel
abstraction-based approach to train DRL systems on finite abstract domains
instead of concrete system states. It yields neural networks whose input states
are finite, making hosting DRL systems directly verifiable using model checking
techniques. Our approach is orthogonal to existing DRL algorithms and
off-the-shelf model checkers. We implement a resulting prototype training and
verification framework and conduct extensive experiments on the
state-of-the-art benchmark. The results show that the systems trained in our
approach can be verified more efficiently while they retain comparable
performance against those that are trained without abstraction.
