Dispatched attention with multi-task learning for nested mention recognition

Entity mentions usually contain other mention in the task of named entity recognition (NER). Nested entities pose challenge to the task of NER. Existing methods fail to sufficiently capture the boundaries information between nested entities, which limits the performance of the task. In this paper, we propose a dispatched attention neural model with multi-task learning for the task. In particular, given an input sentence, a bi-directional Long Short Term Memory (BiLSTM) encodes it as common contextualized hidden representation. Then position and syntax information are leveraged into attention network for capturing mention span features. The attention representation of each task is dispatched to subsequent task to exchange boundaries information for nested mentions. Finally, Conditional Random Fields (CRFs) are used to extract nested mentions in an inside-out order for each task. Results on ACE2005 and GENIA datasets show that the proposed model outperforms state-of-the-art systems, showing its effectiveness in detecting nested mentions. (C) 2019 Elsevier Inc. All rights reserved.