Question-Answering Systems

How does (good) question-answering differ from information retrieval and from information extraction?

Unlike information retrieval...

more syntactic analysis (a bag of words is different from a question!)

more semantic interpretation (sense disambiguation, who's doing what)

as a result, we hope, specific passages from documents, rather than whole documents, can be retrieved and presented.

Unlike information extraction...

questions are more free in form (we're not trying to fill in a few slots in a database)

hence answers will be more freeform, too.