Two-Stage Method for Large-Scale Acquisition of Contradiction Pattern Pairs using Entailment

In this paper we propose a two-stage method to acquire contradiction relations between typed lexico-syntactic patterns such as Xdrug prevents Ydisease and Ydisease caused by Xdrug . In the first stage, we train an SVM classifier to detect contradiction pattern pairs in a large web archive by exploiting the excitation polarity (Hashimoto et al., 2012) of the patterns. In the second stage, we enlarge the first stage classifier’s training data with new contradiction pairs obtained by combining the output of the first stage’s classifier and that of an entailment classifier. We acquired this way 750,000 typed Japanese contradiction pattern pairs with an estimated precision of 80%. We plan to release this resource to the NLP community.