TODEAR: Promoting explainable TKG reasoning through temporal offset enhanced dynamic embedding and adaptive reinforcement learning

Abstract

Recently, Reinforcement Learning (RL) is utilized in Temporal Knowledge Graph (TKG) reasoning to generate analyzable reasoning paths, which achieves explainable reasoning on queries. The process of generating high-quality reasoning paths is facing two major challenges. The first is to construct an efficient entity embedding model from the complex temporal dependencies among entities. The second is to design a fine-grained reward mechanism for the reasoner based on the deep semantics of exploration paths. Motivated by the two challenges, a TKG reasoning framework based on Temporal Offset Enhanced Dynamic Embedding and Adaptive Reinforcement Learning (TODEAR) is proposed in this paper. Firstly, a temporal offset enhanced dynamic embedding model with a distance scoring function is designed to fully exploit the complex temporal dependencies among entities. In order to capture the evolutionary patterns of historical facts, it encodes both the relational structures of the TKG and the temporal offsets between events and queries. Then, a fine-grained adaptive reward mechanism is designed to optimize the reasoner. It generates real-time rewards by analyzing the logic and semantics of exploration paths to mitigate the adverse effects of sparse rewards. Extensive experiments on four benchmark datasets show that TODEAR significantly outperforms the state-of-the-art methods.