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Rhetorical Structure Theory (RST) was originally formulated by Mann and Thompson on 1988.〔http://www.cis.upenn.edu/~nenkova/Courses/cis700-2/rst.pdf〕 This theory was developed as part of studies of computer based text generation. Later people started using it in text summarization and lot of other applications. RST addresses text organization by means of relations that hold between parts of text. It explains coherence by postulating a hierarchical, connected structure of texts. ==Rhetorical relations== Rhetorical relations or coherence relations or discourse relations are paratactic (coordinate) or hypotactic (subordinate) relations that hold across two or more text spans.〔http://www.sfu.ca/~mtaboada/docs/Taboada_Implicit_Explicit.pdf〕 It is widely accepted that notion of coherence is through text relations like this. RST using rhetorical relations provide a systematic way for an analyst to analyse the text. An analysis is usually built by reading the text and constructing a tree using the relations. The following example is a title and summary, appearing at the top of an article in Scientific American magazine (Ramachandran and Anstis, 1986). The original text, broken into numbered units, is:〔http://www.sfu.ca/~mtaboada/docs/Taboada_Mann_RST_Part1.pdf〕 # () The Perception of Apparent Motion # () When the motion of an intermittently seen object is ambiguous # the visual system resolves confusion # by applying some tricks that reflect a bultin knowledge of properties of the physical world In the figure number 1,2,3,4 showing the corresponding units as explained above. Fourth unit and third unit forming a relation 'Means'. Fourth unit is the essential part of this relation. So it is called nucleus of the relation and third unit is called satellite of the relation. Similarly second unit to third and fourth unit is forming relation ′Condition'. All units are also spans and spans may be composed of more than one unit. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rhetorical Structure Theory」の詳細全文を読む スポンサード リンク
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