Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
Statistical ranking methods based on centroid vector (profile) extracted from external knowledge have become widely adopted in the top definitional QA systems in TREC 2003 and 2004. In these approaches, terms in the centroid vector are treated as a bag of words based on the independent assumption. To relax this assumption, this paper proposes a novel language model-based answer reranking method to improve the existing bag-ofwords model approach by considering the dependence of the words in the centroid vector. . | Reranking Answers for Definitional QA Using Language Modeling Yi Chen School of Software Engineering Chongqing University Chongqing China 400044 126cy@126.com Ming Zhou Microsoft Research Asia 5F Sigma Center No.49 Zhichun Road Haidian Bejing China 100080 mingzhou@microsoft.com Shilong Wang College of Mechanical Engineering Chongqing University Chongqing China 400044 slwang@cqu.edu.cn Abstract Statistical ranking methods based on centroid vector profile extracted from external knowledge have become widely adopted in the top definitional QA systems in TREC 2003 and 2004. In these approaches terms in the centroid vector are treated as a bag of words based on the independent assumption. To relax this assumption this paper proposes a novel language model-based answer reranking method to improve the existing bag-of-words model approach by considering the dependence of the words in the centroid vector. Experiments have been conducted to evaluate the different dependence models. The results on the TREC 2003 test set show that the reranking approach with biterm language model significantly outperforms the one with the bag-of-words model and unigram language model by 14.9 and 12.5 respectively in F-Measure 5 . 1 Introduction In recent years QA systems in TREC Text REtrieval Conference have made remarkable progress Voorhees 2002 . The task of TREC QA before 2003 has mainly focused on the factoid questions in which the answer to the question is a number a person name or an organization name or the like. Questions like Who is Colin Powell or What is mold are definitional questions This work was finished while the first author was visiting Microsoft Research Asia during March 2005-March 2006 as a component of the project of AskBill Chatbot led by Dr. Ming Zhou. Voorhees 2003 . Statistics from 2 516 Frequently Asked Questions FAQ extracted from Internet FAQ Archives1 show that around 23.6 are definitional questions. This indicates that definitional questions occur frequently and
