Is there a way to get the subject of a sentence using OpenNLP?

Question

Is there a way to get the subject of a sentence using OpenNLP? I\'m trying to identify the most important part of a users sentence. Generally, users will be submitting sen

Answer 1

Dependency Parser

If you're interested in extracting grammatical relations such as what word or phrase is the subject of a sentence, you should really use a dependency parser. While OpenNLP does support phrase structure parsing, I don't think it does dependency parsing yet.

Opensource Software

Packages written in Java that support dependency parsing include:

• MaltParser
• MSTParser
• Stanford Parser (demo, see typed dependencies section)
• RelEx

Of these, the Stanford Parser is the most accurate. However, some configurations of the MaltParser can be insanely fast (Cer et al. 2010).

Answer 2

For the grammatical subject you'd need to rely on configurational information in the tree. If the parse looks something like (TOP (S (NP ----) (VP ----))) then you can take the NP as the subject; often, though not at all always, that will be the case. However only some sentences will have this configuration; one can easily imagine structures with subjects that are not in that position -- passive constructions, for example.

You're probably better off using MaltParser though.