However, this trend is not entirely unexpected because it is not possible to completely accurately guess syntactic constituents from every substring w. For example, parts of the sentence "in the next 18 minutes" can generate the sequence "in the next CD NN " and " IN DT JJ 18 minutes," but the constituents CD in the former case and DT and JJ in the latter case are not necessary in all situations.
parsing is performed by finding the parse tree T that maximizes the pCFG probability given a sequence of words w ≡ [w 1 , w 2 , • • • , w n ] as shown by Eq.