Consulting other people’s opinions refines our own and helps us choose. Extracting useful information from those opinions, product reviews for instance, is known as sentiment analysis, or opinion mining. Contradiction analysis is the particular case concerned with identifying differing points of view within a body of text.
One of the central tasks is polarity classification: deciding whether a passage takes a positive, negative or neutral stance toward its subject. Contradiction detection builds on top of it, looking for statements about the same aspect of the same object whose polarities disagree, as when one reviewer praises a laptop’s battery and another condemns it.
The hard part is not the classification but the alignment. Two opinions only contradict one another if they are about the same thing, and deciding what counts as the same thing is most of the work.
