Chemical entity recognition in patents by combining dictionary-based and statistical approaches

Akhondi SA, Pons E, Afzal Z, van Haagen H, Becker BFH, Hettne KM, van Mulligen EM, Kors JA

Database 2016:baw061, January 2016
DOI: 10.1093/database/baw061


We describe the development of a chemical entity recognition system and its application in the CHEMDNER patent track of BioCreative 2015. This community challenge includes a Chemical Entity Mention in Patents (CEMP) recognition task and a Chemical Passage Detection (CPD) classification task. We addressed both tasks by an ensemble system that combines a dictionary based approach with a statistical one. For this purpose the performance of several lexical resources was assessed using Peregrine, our open-source indexing engine. We combined our dictionary-based results on the patent corpus with the results of tmChem, a chemical recognizer using a conditional random field classifier. To improve the performance of tmChem, we utilized three additional features, viz. part-of-speech tags, lemmas and word-vector clusters. When evaluated on the training data, our final system obtained an F-score of 85.21% for the CEMP task, and an accuracy of 91.53% for the CPD task. On the test set, the best system ranked sixth among 21 teams for CEMP with an F-score of 86.82%, and second among nine teams for CPD with an accuracy of 94.23%. The differences in performance between the best ensemble system and the statistical system separately were small.

Lay summary


Further info

Click here to view the publication at the journal website