Classifying What-Type Questions by Head Noun Tagging

Classifying what-type questions into proper semantic categories is found more challenging than classifying other types in question answering systems. In this paper, we propose to classify what-type questions by head noun tagging. The approach highlights the role of head nouns as the category discriminator of what-type questions. To reduce the semantic ambiguities of head noun, we integrate local syntactic feature, semantic feature and category dependency among adjacent nouns with Conditional Random Fields (CRFs). Experiments on standard question classification data set show that the approach achieves state-of-the-art performances.