Feature engineering and classical machine learning algorithms such as Hidden Markov Models, Maximum Entropy Models, and Finite State Transducer were the dominant approaches (Nelken and Shieber, 2005;Zitouni et al., 2006;Elshafei et al., 2006).
recent studies show significant improvement using deep neural networks (Belinkov and Glass, 2015;Pham et al., 2017;Orife, 2018).