  In this paper, we propose a new task of sub-event generation for an unseen
process to evaluate the understanding of the coherence of sub-event actions and
objects. To solve the problem, we design SubeventWriter, a sub-event sequence
generation framework with a coherence controller. Given an unseen process, the
framework can iteratively construct the sub-event sequence by generating one
sub-event at each iteration. We also design a very effective coherence
controller to decode more coherent sub-events. As our extensive experiments and
analysis indicate, SubeventWriter can generate more reliable and meaningful
sub-event sequences for unseen processes.
