'SVM+SVM' and 'SVM+RVM' denote two-phase methods using SVM and RVM as the second classifier, respectively. 'SVM' denotes usual SVM using only features f(1). α denotes the coefficient of the domain composition kernel Kc. Note that the accuracy is not defined for NWE because it is unsupervised, and predict protein complexes of various sizes. The precision and recall for NWE were calculated as TP divided by the numbers of predicted and known heterotrimers, respectively.