Patent ID: 7231388

Claim:
A method of retrieving a document from a database, comprising the steps of: extracting a plurality of words contained in a query document received; collecting a plurality of words contained in a plurality of documents, document names of the documents including any of said plurality of words, and an occurring number of words occurring in a document per a language of word registered previously in the database for thereby creating retrieving indexes on the basis of numbers of times said plural words as collected occur in said previously registered documents, respectively, said retrieving indexes being held in a memory; calculating a number of documents registered based on a number of words occurring in a document to obtain weights of said plural words, respectively, acquired in said extracting step through comparison with the words included in said retrieving indexes; selecting a plurality of words on the basis of weight values of said plural words as the condition for selection; calculating degrees of similarity of said plural documents by summing products of the weights and the occurring number of the words registered previously to said query document on the basis of said plurality of selected words; and outputting a result of said degrees of similarity calculated.