Conversational recommender systems (CRS) explicitly solicit users' preferences for improved recommendations on the fly. Most existing CRS solutions employ reinforcement learning methods to train a single policy for a population of users. However, for users new to the system, such a global policy becomes ineffective to produce conversational recommendations, i.e., the cold-start challenge. In this paper, we study CRS policy learning for cold-start users via meta reinforcement learning. We propose to learn a meta policy and adapt it to new users with only a few trials of conversational recommendations. To facilitate policy adaptation, we design three synergetic components. First is a meta-exploration policy dedicated to identify user preferences via exploratory conversations. Second is a Transformer-based state encoder to model a user's both positive and negative feedback during the conversation. And third is an adaptive item recommender based on the embedded states. Extensive experiments on three datasets demonstrate the advantage of our solution in serving new users, compared with a rich set of state-of-the-art CRS solutions.

本文通过基于元强化学习的会话推荐系统策略学习，提出了三个协同的组件，包括专注于识别用户偏好的元探索策略、为每个用户调整项目推荐模块以最大化推荐质量、基于 Transformer 的状态编码器，以在会话期间建模正反馈之间的复杂关系，实现对新用户的快速个性化适应，为冷启动挑战提供解决方案。实验结果表明，与一组最先进的 CRS 解决方案相比，我们的解决方案在为新用户提供服务方面具有优势。

针对冷启动对话推荐的元策略学习