Multi-hop reasoning for incomplete Knowledge Graphs (KGs) demonstrates excellent interpretability with decent performance. Reinforcement Learning (RL) based approaches formulate multi-hop reasoning as a typical sequential decision problem. An intractable shortcoming of multi-hop reasoning with RL is that sparse reward signals make performance unstable. Current mainstream methods apply heuristic reward functions to counter this challenge. However, the inaccurate rewards caused by heuristic functions guide the agent to improper inference paths and unrelated object entities. To this end, we propose a novel adaptive Inverse Reinforcement Learning (IRL) framework for multi-hop reasoning, called AInvR. (1) To counter the missing and spurious paths, we replace the heuristic rule rewards with an adaptive rule reward learning mechanism based on agent’s inference trajectories; (2) to alleviate the impact of over-rewarded object entities misled by inaccurate reward shaping and rules, we propose an adaptive negative hit reward learning mechanism based on agent’s sampling strategy; (3) to further explore diverse paths and mitigate the influence of missing facts, we design a reward dropout mechanism to randomly mask and perturb reward parameters for the reward learning process. Experimental results on several benchmark knowledge graphs demonstrate that our method is more effective than existing multi-hop approaches.

Relation Extraction (RE) is to obtain a predefined relation type of two entities mentioned in a piece of text, e.g., a sentence-level or a document-level text. Most existing studies suffer from the noise in the text, and necessary pruning is of great importance. The conventional sentence-level RE task addresses this issue by a denoising method using the shortest dependency path to build a long-range semantic dependency between entity pairs. However, this kind of denoising method is scarce in document-level RE. In this work, we explicitly model a denoised document-level graph based on linguistic knowledge to capture various long-range semantic dependencies among entities. We first formalize a Syntactic Dependency Tree forest (SDT-forest) by introducing the syntax and discourse dependency relation. Then, the Steiner tree algorithm extracts a mention-level denoised graph, Steiner Graph (SG), removing linguistically irrelevant words from the SDT-forest. We then devise a slide residual attention to highlight word-level evidence on text and SG. Finally, the classification is established on the SG to infer the relations of entity pairs. We conduct extensive experiments on three public datasets. The results evidence that our method is beneficial to establish long-range semantic dependency and can improve the classification performance with longer texts.