INFORMATION RETRIEVAL SYSTEM, INFORMATION RETRIEVING METHOD AND PROGRAM RECORDING MEDIUM FOR INFORMATION RETRIEVAL

摘要

PROBLEM TO BE SOLVED: To improve efficiency by reducing a storage area when a set is large in an information retrieval system which stores the set of data satisfying an assumed retrieval condition and performs retrieval processing. SOLUTION: A condition satisfaction set storing means 33 stores with representation by a complementary set when a set is large and stores with representation by a normal set when it is small. An information updating means 22 updates a condition satisfaction set in accordance with information updation and performs conversion with the representation of the normal set and the representation of the complementary set as necessary by using a complementary set adding means 25 so as to make the sets appropriate representation. It also performs processing that correctly maintains a condition satisfaction set represented by the complementation set when data are added or eliminated. Also, a retrieving means 23 performs a set operation by a method that is suitable for the representation of a set.