Development of an universal open-domain question answering System that can give an answer to any type of real-world questions

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This research aims at developing an Universal Open-domain Question Answering (UQA) System, which returns an answer for any type of real-world questions.First of all, in order to see how many kinds of questions are submitted in the real world, we collected pairs of question and answers in the Web and analyzed them in detail. We investigated one of the WWW question portal community sites, where a user submits a questions to the Web site and another user who see the question can submits the answer of the question. We collected 1,187,873 pairs, each of which consist of a question and a set of its answers, from the Web site. Then, we analyzed 2,064 question-answer pairs selected randomly from the site and annotated the answer types.Next, we started to develop an UQA system by using the result of the analysis. We consider that the correct answer of a question fulfills the following two propositions: (1) it shares the same topic with its question, (2) it has the same answer type as that expected by its question. According to this idea, we implemented the mechanisms that measures the two propositions separately, and then merges their results to give the likelihood to each answer candidates.The developed system was evaluated by using QAC4 test collection, which has been constructed at NTCIR-6 workshop started in 2006 for evaluating the non-factoid question answering. We also conducted the experimental evaluation of finding the answer of real-world questions collected from the Web site. The experimental result showed that, for measuring the proposition (2), the one-classifier approach was effective, which evaluate the matching by using a classifier that detects whether the type from the question side and the type from the answer side match or not.