Architecture
Most modern QA systems use natural language text documents as their underlying knowledge source. Natural language processing techniques are used to both process the question and index or process the text corpus from which answers are extracted. An increasing number of QA systems use the World Wide Web as their corpus of text and knowledge. However, many of these tools do not produce a human-like answer, but rather employ "shallow" methods (keyword-based techniques, templates...) to produce a list of documents or a list of document excerpts containing the probable answer highlighted.
In an alternative QA implementation, human users assemble knowledge in a structured database, called a knowledge base, similar to those employed in the expert systems of the 1970s. It is also to employ a combination of structured databases and natural language text documents in a hybrid QA system. Such a hybrid system may employ data mining algorithms to populate a structured knowledge base that is also populated and edited by human contributors. An example hybrid QA system is the Wolfram Alpha QA system which employs natural language processing to transform human questions into a form that is processed by a curated knowledge base.
Current QA systems typically include a question classifier module that determines the type of question and the type of answer. After the question is analysed, the system typically uses several modules that apply increasingly complex NLP techniques on a gradually reduced amount of text. Thus, a document retrieval module uses search engines to identify the documents or paragraphs in the document set that are likely to contain the answer. Subsequently a filter preselects small text fragments that contain strings of the same type as the expected answer. For example, if the question is "Who invented Penicillin" the filter returns text that contain names of people. Finally, an answer extraction module looks for further clues in the text to determine if the answer candidate can indeed answer the question.
Read more about this topic: Question Answering
Famous quotes containing the word architecture:
“All architecture is great architecture after sunset; perhaps architecture is really a nocturnal art, like the art of fireworks.”
—Gilbert Keith Chesterton (1874–1936)
“For it is not metres, but a metre-making argument, that makes a poem,—a thought so passionate and alive, that, like the spirit of a plant or an animal, it has an architecture of its own, and adorns nature with a new thing.”
—Ralph Waldo Emerson (1803–1882)