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Given the following probabilistic context-free grammar - 

1.NP -> ADJ N [0.6]
2.NP -> N     [0.4] 
3.N  -> cat   [0.2] 
4.N  -> dog   [0.8]

what will be the CNF??

Wasi Ahmad
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Ayesha Khatun Sujana
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    The word "Probabilistic" doesn't have any meaning in this context as you can grab any CFG and convert it to CNF (i.e. in your case you can create drop NP->N and replace it with rules NP-> cat, NP-> dog, and then you adjust your probabilities to 0.4x0.2, and 0.4x0.8). See this for CFG to CNF: https://en.wikipedia.org/wiki/Chomsky_normal_form#Converting_a_grammar_to_Chomsky_normal_form – user3639557 Oct 06 '16 at 00:34
  • yes I did the same (http://stackoverflow.com/questions/39769119/what-will-be-cnf-form-of-this-probabilistic-grammar) but was a little bit confusion, thank you for the suggestion – Ayesha Khatun Sujana Oct 06 '16 at 01:35

2 Answers2

3

Given PCFG in CNF is given below.

1.NP -> ADJ N [0.6]
2.NP -> cat   [0.08] 
3.NP -> dog   [0.32]

Because you need to get the same probability for the result by applying both the original and the converted set of rules (in CNF).

Wasi Ahmad
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0

Be careful! You need to add keep the original rules 3 and 4 with the same probabilities in order for rule 1 to be productive

Jordi
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