How to find out if a sentence is a question (interrogative)?

Question

Is there an open source Java library/algorithm for finding if a particular piece of text is a question or not?
I am working on a question answering system that needs t

Answer 1

In a syntactic parse of a question, the correct structure will be in the form of:

(SBARQ (WH+ (W+) ...)
       (SQ ...*
           (V+) ...*)
       (?))

So, using anyone of the syntactic parsers available, a tree with an SBARQ node having an embedded SQ (optionally) will be an indicator the input is a question. The WH+ node (WHNP/WHADVP/WHADJP) contains the question stem (who/what/when/where/why/how) and the SQ holds the inverted phrase.

i.e.:

(SBARQ 
  (WHNP 
    (WP What)) 
  (SQ 
    (VBZ is) 
    (NP 
      (DT the) 
      (NN question)))
  (. ?))

Of course, having a lot of preceeding clauses will cause errors in the parse (that can be worked around), as will really poorly-written questions. For example, the title of this post "How to find out if a sentence is a question?" will have an SBARQ, but not an SQ.