, d t n : where h(t, k) denotes the parsing history For example, a decision to create a new constituent can be divided in two elementary decisions: deciding to create a constituent and deciding which label to assign to it.
optimally, after each new decision d t k , we should recompute all the means µ t i for all the state vectors S t , t ≤ t. this would make the method intractable, due to the length of derivations in constituent parsing and the interdependence between these means.