I'm currently working on a project for which I have a need to identify certain aspects of a sentence. What markers can I use to algorithmically detect a prepositional phrase in a sentence?

Obviously, I could start by looking for prepositions, but how could I detect the end of the phrase?

1 Answer 1


This can be solved by chunking. NLTK has a rule-based chunker, and the Illinois NLP group has a statistical chunker written using their LBJ machine learning framework.

  • This is very interesting, I'll have to look into it. I was getting worried because I couldn't find any papers or anything on the topic. I began to think Is computational linguistics really so immature that they haven't come up with this basic stuff yet!? Commented Aug 7, 2012 at 0:40
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    CL is relatively new, but I would be surprised if for fifty years nobody wondered how to parse a sentence.
    – jogloran
    Commented Aug 7, 2012 at 0:43
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    Definitely. I'm glad it's immature though, because I had a terrific idea a few weeks ago, I've begun doing the research for it, and it appears both feasible and completely unique. Commented Aug 7, 2012 at 1:01
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    It might be good to find someone in the field that you trust to make sure you're breaking new ground, and that it wasn't that it's called something else in the literature. That said, great ideas are rediscovered all the time -- just look at the history of maximum entropy methods.
    – jogloran
    Commented Aug 7, 2012 at 12:40
  • Oh definitely. I'm waiting to hear back from my linguistics advisor, she's just on vacation. I'm sure she'll refer me to the appropriate person. Commented Aug 7, 2012 at 14:06

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