Text Analysis and Knowledge Extraction

i. Introduction The study of text understanding and knowlegde extraction has been actively done by many researchers. The authors also studied a method of structured information extraction from texts without a global text analysis. The method is available for a comparatively sbort text such as a patent claim clause and an abstract of a technical paper. This paper describes tile outline of a method of knowledge extraction from a longer text which needs a global tex analysis. The kinds of texts ~e expository texts ~) or explanation texts-'. Expository texts described here mean those which have various hierarchical headings such as a title, a heading of each section and sometimes an abstract. In this deEinJtion, most of texts, including technical papers reports and newspapers, are expository. Texts of this kind disclose the main knowledge in a top-down manner and show not only the location of an attribute value in a text but also severn[ key points of the content. This property of expository texts contrasts with that of novels and stories in which an unexpected development of the plot is preferred. This paper pays attention to such characteristics of expository texts and describes a method of anal yzing texts by referring to information contained in the intersentential relations and the headings of texts and then extracting requested knowledge such as a summary from texts in an efficient way.