Keyfact-based text retrieval system, keyfact-based text index method, and retrieval method using this system

PURPOSE: A keyfact-based text search system is provided to display concepts of a document with a couple of an object and property and to index and search text based on the couple-displayed data. CONSTITUTION: In a keyfact-based text search system, a keyfact sampling device(11) samples keyfacts from plural key words having the improved vagueness in speech by analyzing a document group to be searched and question of a user. A keyfact index device(12) saves a keyfact list of the entire document groups in a search structure of keyfact as well as calculates frequency of various keyfacts in the document group to be searched. A keyfact search device(13) receives the key facts about the question of the user and the other ones of the document group. The keyfact search device defines a keyfact-based search model and outputs the similar document to the question by considering a weighting constant depending on the type of keyfacts.