More in detail, given training/testing examples where t 1 i and t 2 i are two AST s and v 1 i and v 2 i are two feature vectors associated with two candidate predicate structures s 1 and s 2 , we define the following kernels: where t j i is the j-th AST of the pair e i , K t is the tree kernel function defined in Section 2 and i, j ∈ {1, 2}.
we adopted the Charniak parse trees available at www.lsi.upc.edu/∼srlconll/ along with the official performance evaluator.