Using Conditional Random Fields to Extract Contexts and Answers of Questions from Online Forums

Proceedings of ACL-08: HLT, pages 710–718, Columbus, Ohio, USA, June 2008. c⃝2008 Association for Computational Linguistics Using Conditional Random Fields to Extract Contexts and Answers of Questions from Online Forums Shilin Ding † ∗ Gao Cong§ † Chin-Yew Lin‡ Xiaoyan Zhu† †Department of Computer Science and Technology, Tsinghua University, Beijing, China §Department of Computer Science, Aalborg University, Denmark ‡Microsoft Research Asia, Beijing, China dingsl@gmail.com gaocong@cs.aau.dk cyl@microsoft.com zxy-dcs@tsinghua.edu.cn Abstract Online forum discussions often contain vast amounts of questions that are the focuses of discussions. Extracting contexts and answers together with the questions will yield not only a coherent forum summary but also a valu- able QA knowledge base. In this paper, we propose a general framework based on Con- ditional Random Fields (CRFs) to detect the contexts and answers of questions from forum threads. We improve the basic framework by Skip-chain CRFs and 2D CRFs to better ac- commodate the features of forums for better performance. Experimental results show that our techniques are very promising. 1 Introduction Forums are web virtual spaces where people can ask questions, answer questions and participate in dis- cussions. The availability of vast amounts of thread discussions in forums has promoted increasing in- terests in knowledge acquisition and summarization for forum threads. Forum thread usually consists of an initiating post and a number of reply posts. The initiating post usually contains several ques- tions and the reply posts usually contain answers to the questions and perhaps new questions. Forum participants are not physically co-present, and thus reply may not happen immediately after questions are posted. The asynchronous nature and multi- participants make multiple questions and answers ∗This work was done when Shilin Ding was a visiting stu- dent at the Microsoft Research Asia †This work was done when Gao Cong worked as a re- searcher at the Microsoft Research Asia. <context id=1>S1: Hi I am looking for a pet friendly hotel in Hong Kong because all of my family is go- ing there for vacation. S2: my family has 2 sons and a dog.</context> <question id=1>S3: Is there any recommended hotel near Sheung Wan or Tsing Sha Tsui?</question> <context id=2,3>S4: We also plan to go shopping in Causeway Bay.</context> <question id=2>S5: What’s the traffic situa- tion around those commercial areas?</question> <question id=3>S6: Is it necessary to take a taxi?</question>. S7: Any information would be ap- preciated. <answer qid=1>S8: The Comfort Lodge near Kowloon Park allows pet as I know, and usually fits well within normal budget. S9: It is also conve- niently located, nearby the Kowloon railway station and subway.</answer> <answer qid=2,3> S10: It’s very crowd in those ar- eas, so I recommend MTR in Causeway Bay because it is cheap to take you around </answer> Figure 1: An example thread with question-context- answer annotated interweaved together, which makes it more difficult to summarize. In this paper, we address the problem of detecting the contexts and answers from forum threads for the questions identified in the same threads. Figure 1 gives an example of a forum …

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