Danescu-Niculescu-Mizil and Lee (2010) (henceforth DL10) extend this approach to Romanian, where a comprehensive list of NPIs is not available, by proposing a bootstrapping approach to co-learn DEOs and NPIs.
the first baseline method proposed by DLD09 simply calculates a ratio of the relative frequencies of a word in NPI contexts versus in a general corpus, and the second is a distillation method which appears to refine the baseline ratios using a task-specific heuristic.