Joint extraction of entities and relations via an entity correlated attention neural model

Abstract

Named entity recognition and relation extraction are crucial tasks in natural language processing. As the traditional pipelined manners may suffer from the error propagation issue and ignore underlying interactions, joint extraction of entities and relations has become the dominant trend. However, the performance of existing joint extraction models needs improvement. This paper presents a two-stage tagging scheme that separately labels candidate head entities and multiple tail entities in specific relations. Next, it proposes a novel lightweight joint extraction neural model based on the entity-first labeling strategy. In the proposed model, the BiLSTM-based encoder combines the hidden state and global context features and feeds them as input for the next two entity labeling tasks. Further, with the input of the mixed context representation, the candidate-head-entity recognition module is adopted to identify the candidate head entity, while the multiple-tail-entities recognition module is equipped with an entity-correlated attention mechanism to identify the corresponding tail entity under a specific head entity. Comprehensive experiments on two widely used English datasets and one self-constructed Chinese dataset were performed. The experimental results showed that the proposed model outperformed the baseline approaches in the relation extraction task and achieved a competitive entity recognition effect via a lightweight architecture.