Hypertext document retrieving apparatus for retrieving hypertext documents relating to each other

A hypertext document retrieving apparatus for retrieving a plurality of particular hypertext documents likely to meet a user's retrieval request from a group of hypertext documents having reference relationships with each other in which one hypertext document having an anchor sentence functions as a parent document for another hypertext document functioning as a reference document and a user refers to one reference document after the user selects one anchor sentence of one parent document corresponding to the reference document, comprising:

• hypertext document table preparing means for preparing hypertext document information, in which one hypertext document identifier identifying one hypertext document, a body of the hypertext document, a parent document identifier identifying a parent document corresponding to the hypertext document functioning as one reference document and an anchor sentence of the parent document are registered, for each of the hypertext documents and preparing a hypertext document table of the hypertext document information for the hypertext documents;
• retrieval index preparing means for recognizing a plurality of words appearing in each of the hypertext documents and the parent documents according to the hypertext document table prepared by the hypertext document table preparing means, recognizing a plurality of occurrence positions of the words in each of the hypertext documents and the parent documents according to the hypertext document table, preparing word information, composed of one or more occurrence document identifiers identifying one or more hypertext documents in which one word appears and occurrence positions of the word in the hypertext documents and one or more anchor sentences of one or more parent documents corresponding to the hypertext documents, for each of the words, and preparing a retrieval index of pieces of word information for the words;
• keyword receiving means for receiving a keyword indicating the user's retrieval request;
• retrieving means for retrieving particular word information corresponding to the keyword received by the keyword receiving means from the retrieval index prepared by the retrieval index preparing means and retrieving a plurality of particular occurrence document identifiers identifying a plurality of particular hypertext documents in which the keyword appears and a plurality of particular occurrence positions of the keyword in the particular hypertext documents and one or more particular anchor sentences of one or more particular parent documents corresponding to the particular hypertext documents from the particular word information;
• document ranking determining means for specifying the particular hypertext documents which are identified by the particular occurrence document identifiers retrieved by the retrieving means, retrieving pieces of particular hypertext document information for the particular hypertext documents from the hypertext document table prepared by the hypertext document table preparing means, unifying one particular hypertext document and one or more particular parent documents corresponding to the particular hypertext document to a unified hypertext document for each of the particular hypertext documents, calculating an occurrence frequency of the keyword in one unified hypertext document for each unified hypertext document, determining a plurality of importance degrees of the unified hypertext documents according to the occurrence frequencies in the unified hypertext documents, setting one importance degree of one unified hypertext document as an importance degree of one particular hypertext document corresponding to the unified hypertext document for each unified hypertext document and determining the ranking of the particular hypertext documents according to the importance degrees of the particular hypertext documents;
• and
• retrieval result displaying means for displaying a plurality of indexes of the particular hypertext documents in a ranked order corresponding to the ranking of the particular hypertext documents determined by the document ranking determining means as a retrieval result.