How to Answer Comparison Questions

'Which city has the larger population, Tokyo or New York?'. To answer the question, in general, we necessarily obtain the prior knowledge about the populations of both cities, and accordingly determine the answer by numeric comparison. Using Machine Reading Comprehension (MRC) to answer such a question has become a popular research topic, which is referred to as a task of Comparison Question Answering (CQA). In this paper, we propose a novel neural CQA model which is trained to answer comparison question. The model is designed as a sophisticated neural network which performs inference in a step-by-step pipeline, including the steps of attentive entity detection (e.g., 'city'), alignment of comparable attributes (e.g., 'population' of the target 'cities'), contrast calculation (larger or smaller), as well as binary classification of positive and negative answers. The experimentation on HotpotQA illustrates that the proposed method achieves an average F1 score of 63.09%, outperforming the baseline with about 10% F1 scores. In addition, it performs better than a series of competitive models, including DecompRC, BERT.