The rule probabilities for each nonterminal A of PCFG G l in language l consist of: 1) θ Al = {θ lAt } t∈{0,1} , where θ lA0 and θ lA1 represent probabilities of choosing the emission rule and the binary production rule, respectively, 2) φ lA = {φ lABC } B,C∈K , where φ lABC represents the probability of nonterminal production A → BC, and 3) ψ lA = {ψ lAw } w∈W l , where ψ lAw represents the probability of terminal emission A → w. , and ψ lAw ≥ 0.
our method does not require any such prior information.