Multi-Granularity Heterogeneous Graph for Document-Level Relation Extraction

Reading text to extract relational facts has been a long-standing goal in natural language processing. It becomes especially challenging when the extraction scope is extended to document level, where multiple entities in a document generally exhibit complex intra- and inter-sentence relations. In this paper, we propose a novel Multi-granularity Heterogeneous Graph (MHG) to tackle this challenge. Specifically, we define four types of nodes with different granularities and eight types of edges based on heuristic rules, entrusting the MHG two major advantages. On the one hand, it connects any two entities with a short path in the graph to better handle the complex inter-sentence interactions between entities. On the other hand, it enables rich interactions among nodes with different granularities to promote accurate multi-hop reasoning. Experimental results on the largest document-level relation extraction dataset suggest that the proposed model achieves new state-of-the-art performance.