Question classification is very important for question answering. This paper presents our research work on automatic question classification through machine learning approaches. We have experimented with five machine learning algorithms: Nearest Neighbors (NN), Naive Bayes (NB), Decision Tree (DT), Sparse Network of Winnows (SNoW), and Support Vector Machines (SVM) using two kinds of features: bag-of-words and bag-of-ngrams. The experiment results show that with only surface text features the SVM outperforms the other four methods for this task. Further, we propose to use a special kernel function called the tree kernel to enable the SVM to take advantage of the syntactic structures of questions. We describe how the tree kernel can be computed efficiently by dynamic programming. The performance of our approach is promising, when tested on the questions from the TREC QA track.

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Question classification using support vector machines

This paper reviews research on automatic summarising in the last decade. This work has grown, stimulated by technology and by evaluation programmes. The paper uses several frameworks to organise the review, for summarising itself, for the factors affecting summarising, for systems, and for evaluation.

The review examines the evaluation strategies applied to summarising, the issues they raise, and the major programmes. It considers the input, purpose and output factors investigated in recent summarising research, and discusses the classes of strategy, extractive and non-extractive, that have been explored, illustrating the range of systems built.

The conclusions drawn are that automatic summarisation has made valuable progress, with useful applications, better evaluation, and more task understanding. But summarising systems are still poorly motivated in relation to the factors affecting them, and evaluation needs taking much further to engage with the purposes summaries are intended to serve and the contexts in which they are used.

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Automatic summarising: The state of the art

To respond correctly to a free form factual question given a large collection of text data, one needs to understand the question to a level that allows determining some of the constraints the question imposes on a possible answer. These constraints may include a semantic classification of the sought after answer and may even suggest using different strategies when looking for and verifying a candidate answer. This work presents a machine learning approach to question classification. Guided by a layered semantic hierarchy of answer types, we develop a hierarchical classifier that classifies questions into fine-grained classes. This work also performs a systematic study of the use of semantic information sources in natural language classification tasks. It is shown that, in the context of question classification, augmenting the input of the classifier with appropriate semantic category information results in significant improvements to classification accuracy. We show accurate results on a large collection of free-form questions used in TREC 10 and 11.

Learning question classifiers: the role of semantic information

A survey on question answering technology from an information retrieval perspective

We describe the overall organization of the CLEF 2003 evaluation campaign, with a particular focus on the cross-language ad hoc and domainspecific retrieval tracks. The paper discusses the evaluation approach adopted, describes the tracks and tasks offered and the test collections used, and provides an outline of the guidelines given to the participants. It concludes with an overview of the techniques employed for results calculation and analysis for the monolingual, bilingual and multilingual and GIRT tasks.

/pdf/comparative-evaluation-of-multilingual-information-access-4ai1xl16m2.pdf

Comparative Evaluation of Multilingual Information Access Systems

Web-based search engines such as Google and NorthernLight return documents that are relevant to a user query, not answers to user questions. We have developed an architecture that augments existing search engines so that they support natural language question answering. The process entails five steps: query modulation, document retrieval, passage extraction, phrase extraction, and answer ranking. In this paper we describe some probabilistic approaches to the last three of these stages. We show how our techniques apply to a number of existing search engines and we also present results contrasting three different methods for question answering. Our algorithm, probabilistic phrase reranking (PPR) using proximity and question type features achieves a total reciprocal document rank of .20 on the TREC 8 corpus. Our techniques have been implemented as a Web-accessible system, called NSIR.

/pdf/probabilistic-question-answering-on-the-web-306armejh2.pdf

Probabilistic question answering on the web

Web-based search engines such as Google and NorthernLight return documents that are relevant to a user query, not answers to user questions. We have developed an architecture that augments existing search engines so that they support natural language question answering. The process entails five steps: query modulation, document retrieval, passage extraction, phrase extraction, and answer ranking. In this article, we describe some probabilistic approaches to the last three of these stages. We show how our techniques apply to a number of existing search engines, and we also present results contrasting three different methods for question answering. Our algorithm, probabilistic phrase reranking (PPR), uses proximity and question type features and achieves a total reciprocal document rank of .20 on the TREC8 corpus. Our techniques have been implemented as a Web-accessible system, called NSIR.

/pdf/probabilistic-question-answering-on-the-web-3bpd5s91vb.pdf

Probabilistic question answering on the Web

Web-based search engines such as Google and NorthernLight return documents that are relevant to a user query, not answers to user questions. We have developed an architecture that augments existing search engines so that they support natural language question answering. The process entails five steps: query modulation, document retrieval, passage extraction, phrase extraction, and answer ranking. In this article, we describe some probabilistic approaches to the last three of these stages. We show how our techniques apply to a number of existing search engines, and we also present results contrasting three different methods for question answering. Our algorithm, probabilistic phrase reranking (PPR), uses proximity and question type features and achieves a total reciprocal document rank of .20 on the TREC8 corpus. Our techniques have been implemented as a Web-accessible system, called NSIR. © 2005 Wiley Periodicals, Inc.

Probabilistic question answering on the Web: Research Articles

This study examines the usefulness of common off the shelf compression software such as gzip in enhancing already existing summaries and producing summaries from scratch. Since the gzip algorithm works by removing repetitive data from a file in order to compress it, we should be able to determine which sentences in a summary contain the least repetitive data by judging the gzipped size of the summary with the sentence compared to the gzipped size of the summary without the sentence. By picking the sentence that increased the size of the summary the most, we hypothesized that the summary will gain the sentence with the most new information. This hypothesis was found to be true in many cases and to varying degrees in this study.

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Amardeep Grewal

Papers

Probabilistic question answering on the web

Probabilistic question answering on the Web

Probabilistic question answering on the Web: Research Articles

Multi-document summarization using off the shelf compression software