Deformable Stacked Structure for Named Entity Recognition
Table 6: Effects of different structure setting on OntoNotes 5.0 datset. Structure 1: deformable stacked structure between LSTM layers. Structure 2: deformable stacked structure between LSTM layers and CRF. Structure 3: both structure 1 and structure 2.
['[BOLD] Structure', '[BOLD] # of offsets', '[BOLD] P', '[BOLD] R', '[BOLD] F']
These two structures differ on the function of their next layers, and the difference in improvement also comes from that. For structure 1, the deformable stacked structure reconstructs the input of the next LSTM layer. Thus, it plays a role of feature augmentation for the next LSTM layer to better extract related information. And better extraction of feature also helps with the decoding procedure. For structure 2, the deformable stacked structure reconstructs the input of the CRF layer and plays a role of feature selection for decoding. Compared with the baseline model, the deformable stacked structure has great improvement in recall. It indicates that the deformable stacked structure can discover more named entity in the sentence.