Some of these predictors, including the identity -or even number (McClosky, 2008) -of alreadygenerated siblings, can be prohibitively expensive in sentences above a short length k. For example, they break certain modularity constraints imposed by the charts used in O(k 3 )-optimized algorithms (Paskin, 2001a;Eisner, 2000).
in bottom-up parsing and training from text, everything about the yield -i.e., the ordered sequence of all already-generated descendants, on the side of the head that is in the process of spawning off an additional child -is not only known but also readily accessible.