Abstract
Our legal question answering system combines legal information retrieval and textual entailment, and exploits paraphrasing and sentence-level analysis of queries and legal statutes. We have evaluated our system using the training data from the competition on legal information extraction/entailment (COLIEE)-2016. The competition focuses on the legal information processing required to answer yes/no questions from Japanese legal bar exams, and it consists of three phases: legal ad-hoc information retrieval (Phase 1), textual entailment (Phase 2), and a combination of information retrieval and textual entailment (Phase 3). Phase 1 requires the identification of Japan civil law articles relevant to a legal bar exam query. For this phase, we have used an information retrieval approach using TF-IDF and a Ranking SVM. Phase 2 requires decision on yes/no answer for previously unseen queries, which we approach by comparing the approximate meanings of queries with relevant articles. Our meaning extraction process uses a selection of features based on a kind of paraphrase, coupled with a condition/conclusion/exception analysis of articles and queries. We also identify synonym relations using word embedding, and detect negation patterns from the articles. Our heuristic selection of attributes is used to build an SVM model, which provides the basis for ranking a decision on the yes/no questions. Experimental evaluation show that our method outperforms previous methods. Our result ranked highest in the Phase 3 in the COLIEE-2016 competition.
Notes
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Lucene can be downloaded from http://lucene.apache.org/core/.
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The SVM function in Weka is provided by libsvm https://www.csie.ntu.edu.tw/~cjlin/libsvm/, and the linear kernal is from liblinear https://www.csie.ntu.edu.tw/~cjlin/liblinear/.
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Acknowledgements
This research was supported by the Alberta Machine Intelligence Institute (www.amii.ca). We are indebted to Ken Satoh of the National Institute for Informatics, who had the vision to create the COLIEE competition.
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Kim, MY., Xu, Y., Lu, Y., Goebel, R. (2017). Question Answering of Bar Exams by Paraphrasing and Legal Text Analysis. In: Kurahashi, S., Ohta, Y., Arai, S., Satoh, K., Bekki, D. (eds) New Frontiers in Artificial Intelligence. JSAI-isAI 2016. Lecture Notes in Computer Science(), vol 10247. Springer, Cham. https://doi.org/10.1007/978-3-319-61572-1_20
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