A Civil Code Article Information Retrieval System based on Phrase Alignment with Article Structure Analysis and Ensemble Approach

In this paper, we introduce a system for COLIEE task phase 1 that retrieves relevant civil code article(s) for making correct entailment to the questions of Japanese Bar Exam. This system is an extended version of our previous system that based on legal terminology and civil code article structure. However, the performance of the previous system is not as good as best performance system of the task. In this paper, we introduce concept of phrase alignment that takes into account the civil code article structure. In addition, due to the variations of the question types, the settings that are good for particular type of questions may not be good for other types of questions. Therefore, we propose to use systems with different settings and generate final answer by aggregating the output of different systems based on ensemble approach. Finally, we also discuss the difference between English task and Japanese task based on the retrieval results of Indri, one of the state-of-the-art information retrieval system.