Application of cascade binary pointer tagging in joint entity and relation extraction of Chinese medical text.

Extracting relational triples from unstructured medical texts can provide a basis for the construction of large-scale medical knowledge graphs. The cascade binary pointer tagging network (CBPTN) shows excellent performance in the joint entity and relation extraction, so we try to explore its effectiveness in the joint entity and relation extraction of Chinese medical texts. In this paper, we propose two models based on the CBPTN: CBPTN with conditional layer normalization (Cas-CLN) and biaffine transformation-based CBPTN with multi-head selection (BTCAMS). Cas-CLN uses the CBPTN to decode the head entity and relation-tail entity successively and utilizes conditional layer normalization to enhance the connection between the two steps. BTCAMS detects all possible entities in a sentence by using the CBPTN and then determines the relation between each entity pair through biaffine transformation. We test the performance of the two models on two Chinese medical datasets: CMeIE and CEMRDS. The experimental results prove the effectiveness of the two models. Compared with the baseline CasREL, the F1 value of Cas-CLN and BTCAMS on the test data of CMeIE improved by 1.01 and 2.13%; on the test data of CEMRDS, the F1 value improved by 1.99 and 0.68%.