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The 1970s and 1980s saw the development of comprehensive theories in [[computational linguistics]], which led to the development of ambitious projects in text comprehension and question answering. One example of such a system was the Unix Consultant (UC), developed by [[Robert Wilensky]] at [[University of California, Berkeley|U.C. Berkeley]] in the late 1980s. The system answered questions pertaining to the [[Unix]] operating system. It had a comprehensive hand-crafted knowledge base of its domain, and it aimed at phrasing the answer to accommodate various types of users. Another project was LILOG, a [[natural language understanding|text-understanding]] system that operated on the domain of tourism information in a German city. The systems developed in the UC and LILOG projects never went past the stage of simple demonstrations, but they helped the development of theories on computational linguistics and reasoning. |
The 1970s and 1980s saw the development of comprehensive theories in [[computational linguistics]], which led to the development of ambitious projects in text comprehension and question answering. One example of such a system was the Unix Consultant (UC), developed by [[Robert Wilensky]] at [[University of California, Berkeley|U.C. Berkeley]] in the late 1980s. The system answered questions pertaining to the [[Unix]] operating system. It had a comprehensive hand-crafted knowledge base of its domain, and it aimed at phrasing the answer to accommodate various types of users. Another project was LILOG, a [[natural language understanding|text-understanding]] system that operated on the domain of tourism information in a German city. The systems developed in the UC and LILOG projects never went past the stage of simple demonstrations, but they helped the development of theories on computational linguistics and reasoning. |
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Recently, specialized natural language QA systems have been developed, such as [http://bitem.hesge.ch/content/eagli-eagle-eye EAGLi] for health and life scientists. |
Recently, specialized natural language QA systems have been developed, such as [http://bitem.hesge.ch/content/eagli-eagle-eye EAGLi] for health and life scientists, and [[Wolfram Alpha]], an online computational knowledge engine that answers factual queries directly by computing the answer from externally sourced curated data. |
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==Architecture== |
==Architecture== |
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Revision as of 20:43, 15 January 2019
Question answering (QA) is a computer science discipline within the fields of information retrieval and natural language processing (NLP), which is concerned with building systems that automatically answer questions posed by humans in a natural language.[1]
Overview
A QA implementation, usually a computer program, may construct its answers by querying a structured database of knowledge or information, usually a knowledge base. More commonly, QA systems can pull answers from an unstructured collection of natural language documents.
Some examples of natural language document collections used for QA systems include:
- a local collection of reference texts
- internal organization documents and web pages
- compiled newswirereports
- a set of Wikipedia pages
- a subset of World Wide Web pages
QA research attempts to deal with a wide range of question types including: fact, list, definition, How, Why, hypothetical, semantically constrained, and cross-lingual questions.
- Closed-domain question answering deals with questions under a specific domain (for example, medicine or automotive maintenance), and can be seen as an easier task because NLP systems can exploit domain-specific knowledge frequently formalized in descriptive rather than procedural information. QA systems in the context of machine reading applications have also been constructed in the medical domain, for instance related to Alzheimers disease[2]
- Open-domainquestion answering deals with questions about nearly anything, and can only rely on general ontologies and world knowledge. On the other hand, these systems usually have much more data available from which to extract the answer.
History
 |
Two early QA systems were BASEBALL
SHRDLU was a highly successful question-answering program developed by Terry Winograd in the late 60s and early 70s. It simulated the operation of a robot in a toy world (the "blocks world"), and it offered the possibility of asking the robot questions about the state of the world. Again, the strength of this system was the choice of a very specific domain and a very simple world with rules of physics that were easy to encode in a computer program.
In the 1970s,
The 1970s and 1980s saw the development of comprehensive theories in
Recently, specialized natural language QA systems have been developed, such as EAGLi for health and life scientists, and
Architecture
As of 2001, QA systems typically included a question classifier module that determines the type of question and the type of answer.[5] A multiagent question-answering architecture has been proposed, where each domain is represented by an agent which tries to answer questions taking into account its specific knowledge; a meta–agent controls the cooperation between question answering agents and chooses the most relevant answer(s).[6]
Question answering methods
QA is very dependent on a good search corpus - for without documents containing the answer, there is little any QA system can do. It thus makes sense that larger collection sizes generally lend well to better QA performance, unless the question domain is orthogonal to the collection. The notion of data redundancy in massive collections, such as the web, means that nuggets of information are likely to be phrased in many different ways in differing contexts and documents,[7] leading to two benefits:
- By having the right information appear in many forms, the burden on the QA system to perform complex NLP techniques to understand the text is lessened.
- Correct answers can be filtered from false positivesby relying on the correct answer to appear more times in the documents than instances of incorrect ones.
Some question answering systems rely heavily on automated reasoning.[8][9] There are a number of question answering systems designed in Prolog,[10] a logic programming language associated with artificial intelligence.
Open domain question answering
|
In
The system takes a natural language question as an input rather than a set of keywords, for example, "When is the national day of China?" The sentence is then transformed into a query through its logical form. Having the input in the form of a natural language question makes the system more user-friendly, but harder to implement, as there are various question types and the system will have to identify the correct one in order to give a sensible answer. Assigning a question type to the question is a crucial task, the entire answer extraction process relies on finding the correct question type and hence the correct answer type.
Keyword extraction is the first step for identifying the input question type. In some cases, there are clear words that indicate the question type directly. i.e. "Who", "Where" or "How many", these words tell the system that the answers should be of type "Person", "Location", "Number" respectively. In the example above, the word "When" indicates that the answer should be of type "Date". POS (Part of Speech) tagging and syntactic parsing techniques can also be used to determine the answer type. In this case, the subject is "Chinese National Day", the predicate is "is" and the adverbial modifier is "when", therefore the answer type is "Date". Unfortunately, some interrogative words like "Which", "What" or "How" do not give clear answer types. Each of these words can represent more than one type. In situations like this, other words in the question need to be considered. First thing to do is to find the words that can indicate the meaning of the question. A lexical dictionary such as WordNet can then be used for understanding the context.
Once the question type has been identified, an Information retrieval system is used to find a set of documents containing the correct key words. A tagger and NP/Verb Group chunker can be used to verify whether the correct entities and relations are mentioned in the found documents. For questions such as "Who" or "Where", a Named Entity Recogniser is used to find relevant "Person" and "Location" names from the retrieved documents. Only the relevant paragraphs are selected for ranking.
A vector space model can be used as a strategy for classifying the candidate answers. Check if the answer is of the correct type as determined in the question type analysis stage. Inference technique can also be used to validate the candidate answers. A score is then given to each of these candidates according to the number of question words it contains and how close these words are to the candidate, the more and the closer the better. The answer is then translated into a compact and meaningful representation by parsing. In the previous example, the expected output answer is "1st Oct."
Issues
In 2002, a group of researchers presented an unpublished and largely unsourced report as a funding support document, in which they describe a 5-year roadmap of research current to the state of the question answering field at that time.
Progress
QA systems have been extended in recent years to encompass additional domains of knowledge[11] For example, systems have been developed to automatically answer temporal and geospatial questions, questions of definition and terminology, biographical questions, multilingual questions, and questions about the content of audio, images, and video. Current QA research topics include:
- interactivity—clarification of questions or answers
- answer reuse or caching
- answer presentation[12]
- knowledge representation and reasoning
- social media analysis with QA systems
- sentiment analysis[13]
- utilization of thematic roles[14]
- semantic resolution: to bridge the gap between syntactically different questions and answer-bearing texts[15]
- utilization of linguistic resources,[16] such as WordNet, FrameNet, and the similar
IBM's question answering system,
References
- ISBN 978-1-60845-990-2.
- ^ Roser Morante, Martin Krallinger, Alfonso Valencia and Walter Daelemans. Machine Reading of Biomedical Texts about Alzheimer's Disease. CLEF 2012 Evaluation Labs and Workshop. September 17, 2012
- ^ GREEN JR, Bert F; et al. (1961). "Baseball: an automatic question-answerer" (PDF). Western joint IRE-AIEE-ACM computer conference: 219–224.
- ^ Woods, William A; Kaplan, R. (1977). "Lunar rocks in natural English: Explorations in natural language question answering". Linguistic structures processing 5. 5: 521–569.
- ^ Hirschman, L. & Gaizauskas, R. (2001) Natural Language Question Answering. The View from Here. Natural Language Engineering (2001), 7:4:275-300 Cambridge University Press.
- .
- ^ Lin, J. (2002). The Web as a Resource for Question Answering: Perspectives and Challenges. In Proceedings of the Third International Conference on Language Resources and Evaluation (LREC 2002).
- ^ Moldovan, Dan, et al. "Cogex: A logic prover for question answering." Proceedings of the 2003 Conference of the North American Chapter of the Association for Computational Linguistics on Human Language Technology-Volume 1. Association for Computational Linguistics, 2003.
- ^ Furbach, Ulrich, Ingo Glöckner, and Björn Pelzer. "An application of automated reasoning in natural language question answering." Ai Communications 23.2-3 (2010): 241-265.
- )
- ^ Maybury, M. T. editor. 2004. New Directions in Question Answering. AAAI/MIT Press.
- ^ Perera, R., Nand, P. and Naeem, A. 2017. Utilizing typed dependency subtree patterns for answer sentence generation in question answering systems.
- ^ "BitCrawl by Hobson Lane". Archived from the original on October 27, 2012. Retrieved 2012-05-29.
{{cite web}}: Unknown parameter|deadurl=ignored (|url-status=suggested) (help) - ^ Perera, R. and Perera, U. 2012. Towards a thematic role based target identification model for question answering.
- ^ Bahadorreza Ofoghi; John Yearwood; Liping Ma (2008). The impact of semantic class identification and semantic role labeling on natural language answer extraction. The 30th European Conference on Information Retrieval (ECIR'08). Springer Berlin Heidelberg. pp. 430–437.
{{cite conference}}: Unknown parameter|last-author-amp=ignored (|name-list-style=suggested) (help) - doi:10.1002/asi.20989.)
{{cite journal}}: Unknown parameter|last-author-amp=ignored (|name-list-style=suggested) (help - ^ https://www.nytimes.com/2011/02/17/science/17jeopardy-watson.html?_r=0
- ^ https://research.fb.com/downloads/drqa/
- arXiv:1704.00051 [cs.CL].
Further reading
- Dragomir R. Radev, John Prager, and Valerie Samn. Ranking suspected answers to natural language questions using predictive annotation. In Proceedings of the 6th Conference on Applied Natural Language Processing, Seattle, WA, May 2000.
- John Prager, Eric Brown, Anni Coden, and Dragomir Radev. Question-answering by predictive annotation. In Proceedings, 23rd Annual International ACM SIGIR Conference on Research and Development in Information Retrieval, Athens, Greece, July 2000.
- ISBN 0-12-362830-X.
- L. Fortnow, Steve Homer (2002/2003). A Short History of Computational Complexity. In D. van Dalen, J. Dawson, and A. Kanamori, editors, The History of Mathematical Logic. North-Holland, Amsterdam.