  Recent curriculum Reinforcement Learning (RL) has shown notable progress in
solving complex tasks by proposing sequences of surrogate tasks. However, the
previous approaches often face challenges when they generate curriculum goals
in a high-dimensional space. Thus, they usually rely on manually specified goal
spaces. To alleviate this limitation and improve the scalability of the
curriculum, we propose a novel curriculum method that automatically defines the
semantic goal space which contains vital information for the curriculum
process, and suggests curriculum goals over it. To define the semantic goal
space, our method discretizes continuous observations via vector
quantized-variational autoencoders (VQ-VAE) and restores the temporal relations
between the discretized observations by a graph. Concurrently, ours suggests
uncertainty and temporal distance-aware curriculum goals that converges to the
final goals over the automatically composed goal space. We demonstrate that the
proposed method allows efficient explorations in an uninformed environment with
raw goal examples only. Also, ours outperforms the state-of-the-art curriculum
RL methods on data efficiency and performance, in various goal-reaching tasks
even with ego-centric visual inputs.
