, l m−1 , and ρ is the log probability of the first m−1 righthand symbols, and the logical form is x where f m (x ) = x.
we can write I (Du,l u ,l u+1 ) + O (C,i ,j ,x ) , but this is not possible by the definition of O (A,i,j,x) in equation 7, as we would have found a derivation with a strictly better objective.