In this paper, we present a deep reinforcement learning (RL) framework for iterative dialog policy optimization in end-to-end task-oriented dialog systems. Popular approaches in learning dialog policy with RL include letting a dialog agent to learn against a user simulator. Building a reliable user simulator, however, is not trivial, often as difficult as building a good dialog agent. We address this challenge by jointly optimizing the dialog agent and the user simulator with deep RL by simulating dialogs between the two agents. We first bootstrap a basic dialog agent and a basic user simulator by learning directly from dialog corpora with supervised training. We then improve them further by letting the two agents to conduct task-oriented dialogs and iteratively optimizing their policies with deep RL. Both the dialog agent and the user simulator are designed with neural network models that can be trained end-to-end. Our experiment results show that the proposed method leads to promising improvements on task success rate and total task reward comparing to supervised training and single-agent RL training baseline models.

本文提出一种采用深度强化学习框架实现的迭代式对话策略优化方法，解决了当前学习对话策略的主流方法之一 - 与用户模拟器进行对话时模拟器可靠性低的难题，同时也极大地提高了任务成功率与任务奖励值。此方法可以广泛应用于端到端任务导向型对话系统中，其关键在于通过深度RL来同时优化对话代理和用户模拟器的对话策略，并且对话代理和用户模拟器均建立在端到端的神经网络模型上。

端到端可训练任务导向神经对话模型中的迭代策略学习