Overview of main components
The textual question answering system has four main components:question analysis, document retrieval, document analysis and answer selection.
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Given a natural language question posed by a user, the first step is to analyze the question itself. The question analysis component may include a morph-syntactic analysis of the question. The question is also classified to determine what it is asking for. Depending on the morph-syntactic analysis and the class of the question, a retrieval query is formulated which is posed to the retrieval component.
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The retrieval component is generally a standard document retrieval system which identifies documents that contain terms from a given query. The retrieval component returns a set or ranked list of documents that are further analyzed by the document analysis component.
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The document analysis component takes as input documents that are likely to contain an answer to the original question, together with a specification of what types of phrases should count as correct answers. This specification is generated by the question analysis component. This component extracts a number of candidate answers which are sent to the answer selection component.
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The answer selection component selects the phrase that is most likely to be a correct answer from a number of phrases of the appropriate type, as specified by the question analysis component. It returns the final answer or a ranked list of answers to the user.
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The main components are displayed in the pictures below.
