Extract imperative sentences from a document(English) using NLP in python

Question

I am very new to NLP, hence require some help on extracting imperative sentences from a document. I am working on a project where I need to get all the imperative sentences from the entire document(English documents). I understand I need to use POS tagging. But how do I proceed further.

Thanks.

Answer 1

In order to maximize accuracy you would need to use not only a POS tagger but also a syntactic parser. Nevertheless for this task POS tags can probably give you reasonable results indeed, here is a general method:

1. Segment the data into sentences and tokens
2. Apply the POS tagger (it predicts a POS tag for every token)
3. A sentence is (likely) imperative if the following conditions are satisfied:
   • the sentence ends with a full stop or exclamation mark
   • the POS for the first token corresponds to a verb

This heuristic is probably all you need, but if you want to go further you could generate instances containing these features (and possibly add a few others) for every sentence, annotate a training set and train a supervised model.