In order to capture the inter-dependencies between triggers and argument roles, we introduce memory vectors/matrices to store the prediction information during the course of labeling the sentences.
after that, higher level features has been investigated to improve the performance (Ji and Grishman, 2008;Gupta and Ji, 2009;Patwardhan and Riloff, 2009;Liao and Grishman, 2010;Liao and Grishman, 2011;Hong et al., 2011;McClosky et al., 2011;Huang and Riloff, 2012;Li et al., 2013).