Structured Refinement for Sequential Labeling

Filtering target-irrelevant information through hierarchically refining hidden states has been demonstrated to be effective for obtaining informative representations. However, previous work simply relies on locally normalized attention without considering possible labels at other time steps, the capacity for modeling long-term dependency relations is thus limited. In this paper, we propose to extend previous work with globally normalized attention, e.g., structured attention, to leverage structural information for more effective representation refinement. We also propose two implementation tricks to accelerate CRF computation and an initialization trick for Chinese character embeddings to further improve performance. We provide extensive experimental results on various datasets to show the effectiveness and efficiency of our proposed method.