We extended this PMI score to semantic arguments instead of syntactic dependencies.
the value for this feature is computed as follows: We computed Equation (2) by applying verbal SRL (Punyakanok, Roth, and Yih 2008), nominal SRL (Gerber, Chai, and Meyers 2009), and coreference identification (OpenNLP) to the Gigaword corpus (Graff 2003); because these tools are not fast enough to process all 1,000,000 documents in the corpus, however, we selected subsets of the corpus for each p 1 /p 2 combination observed in our implicit argument data.