To train a classifier on instances containing the original 31 features and SRCTs, we employ SVM light−T K (Moschitti, 2004;Moschitti, 2006), which (1) trains an SVM classifier using the 31 features with a linear kernel; (2) trains an SVM classifier using only the SRCTs with a convolution  kernel; and (3) combines these two kernels using a composite kernel.
we define composite kernel K c for combining linear kernel K l and convolution kernel K t as follows: where F 1 and F 2 are the set of 31 features from two training instances, T 1 and T 2 are their SRCTs, and T is the combination parameter.