COLIEE 2017:Papers with Abstracts

Abstract. We present the evaluation of the legal question answering Competition on Legal Information Extraction/Entailment (COLIEE) 2017. The COLIEE 2017 Task consists of two sub-Tasks: legal information retrieval (Task 1), and recognizing entailment between articles and queries (Task 2). Participation was open to any group based on any approach, and the tasks attracted 10 teams. We received 9 submissions to Task 1 (for a total of 17 runs), and 8 submissions to Task 2 (for a total of 20 runs).
Abstract. 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.
Abstract. Despite growing needs of the legal artificial intelligence (AI), its development is slower than other AI domains because legal expertise is essentially required to develop legal AI systems. Legal knowledge representation on legal expertise needs to be considered to implement legal reasoning AI systems. In this paper, we present a legal reasoning methodology, which utilizes multiple expert knowledge based agents. These agents are designed to solve recognizing textual entailment (RTE) problems with syntactic and interpretative knowledge. The validity of the proposed method is provided through experiments with the COLIEE 2017 data.
Abstract. This paper presents an end-to-end question answering system for legal texts. This system includes two main phases. In the first phase, our system will retrieve articles from Japanese Civil Code that are relevant with the given question using the cosine distance after the given question and articles are converted into vectors using TF-IDF weighting scheme. Then, a ranking model can be applied to re-rank these retrieved articles using a learning to rank algorithm and annotated corpus. In the second phase, we adapted two deep learning models, which has been proposed for the Natural language inference task, to check the entailment relationship between a question and its related articles including a sentence encoding-based model and a decomposable attention model. Experimental results show that our approaches can be a promising approach for information extraction/entailment in legal texts.
Abstract. Legal professionals worldwide are currently trying to get up-to-pace with the explosive growth in legal document availability through digital means. This drives a need for high efficiency Legal Information Retrieval (IR) and Question Answering (QA) methods. The IR task in particular has a set of unique challenges that invite the use of semantic motivated NLP techniques. In this work, a two-stage method for Legal Information Retrieval is proposed, combining lexical statistics and distributional sentence representations in the context of Competition on Legal Information Extraction/Entailment (COLIEE). The combination is done with the use of disambiguation rules, applied over the rankings obtained through n-gram statistics. After the ranking is done, its results are evaluated for ambiguity, and disambiguation is done if a result is decided to be unreliable for a given query. Competition and experimental results indicate small gains in overall retrieval performance using the proposed approach. Additionally, an analysis of error and improvement cases is presented for a better understanding of the contributions.
Abstract. A central issue of yes/no question answering is usage of knowledge source given a question. While yes/no question answering has been studied for a long time, legal yes/no question answering largely differs from other domains. The most distinguishing characteristic is that legal issues require precise linguistic analysis such as predicates, case-roles, conditions, etc. We have developed a yes/no question answer-ing system for answering questions in a legal domain. Our system uses linguistic analysis, in order to find correspondences of predicates and arguments given problem sentences and knowledge source sentences. We applied our system to the COLIEE (Competition on Legal Information Extraction/Entailment) 2017 task. Our team shared the second place in this COLIEE 2017 Phase Two task, which asks to answer yes or no given a problem sentence. This result shows that precise linguistic analyses are effective even without the big data approach with machine learning, rather better in its analyzable design for future improvements.
Abstract. This paper presents a description about our adopted approach for the information retrieval and textual entailment tasks of the COLIEE 2017 competition. We address the information retrieval task by implementing a partial string matching and a topic clustering method. For the textual entailment task, we propose a Long Short-Term Memory (LSTM) - Convolutional Neural Network (CNN) model which utilizes word embeddings trained on the Google News vectors. We evaluated our approach for both tasks on the COLIEE 2017 dataset. The results demonstrate that the topic clustering method outperformed the partial string matching method in the information retrieval task. The performance of LSTM-CNN model was competitive with other textual entailment systems.
Abstract. This year’s COLIEE has two tasks called phases 1 and 2. The phase 1 needs to find the relevant article given a query t2, and the phase 2 needs to answer whether the given query t2 is yes or no according to Japan civil law articles.
This paper presents our proposals for the phase 2 task. Two methods are presented. The first goes along the standard method taken by many authors, such that the relevant article t1 is selected by the similarity to the query t2 at the requirement (condition) and the effect (conclusion) descriptions of the articles. The second is our new proposal, in which Neural Networks with attention mechanism are applied to all the civil law articles in deciding the truthness of the query t2. This method takes into account all the articles by properly calculating their weighted sum.