Temporal knowledge graph (TKG) reasoning is a crucial task that has gained increasing research interest in recent years. Most existing methods focus on reasoning at past timestamps to complete the missing facts, and there are only a few works of reasoning on known TKGs to forecast future facts. Compared with the completion task, the forecasting task is more difficult that faces two main challenges: (1) how to effectively model the time information to handle future timestamps? (2) how to make inductive inference to handle previously unseen entities that emerge over time? To address these challenges, we propose the first reinforcement learning method for forecasting. Specifically, the agent travels on historical knowledge graph snapshots to search for the answer. Our method defines a relative time encoding function to capture the timespan information, and we design a novel time-shaped reward based on Dirichlet distribution to guide the model learning. Furthermore, we propose a novel representation method for unseen entities to improve the inductive inference ability of the model. We evaluate our method for this link prediction task at future timestamps. Extensive experiments on four benchmark datasets demonstrate substantial performance improvement meanwhile with higher explainability, less calculation, and fewer parameters when compared with existing state-of-the-art methods.

本文提出了一种基于强化学习的方法来进行时态知识图推理，该方法解决了建模未来时间信息以及处理先前未见实体的归纳推理的问题，通过在历史知识图上搜索答案，设计了相对时间编码函数以及基于Dirichlet分布的时间-shaped奖励机制，并提出了一种新颖的表示方法来提高模型的归纳推理能力，在四个基准数据集上获得了较大的性能改进。

TimeTraveler: 针对时间知识图谱预测的增强学习