The actual grammar rules and associated probabilities that we use in defining our syntactic module are derived from the WSJ corpus of the Penn Treebank by maximumlikelihood estimation.
for each rule N → φ used in the treebank, we add the rule to the grammar and set its probability to C(N→φ) ψ C(N→ψ) , where C(•) denotes the "count" or a rule (i.e., the number of times it is used in the corpus).