Since the parse tree is defined by a sequence of transition actions a, we write p(x, y) as p(x, a).
3 The joint distribution p(x, a) is factorized into a sequence of transition probabilities and terminal probabilities (when actions are GEN), which are parametrized by a transitional state embedding u: where I is an indicator function and u t represents the state embedding at time step t. the conditional probability of the next action is: where a t represents the action embedding at time step t, A the action space and b a the bias.