Hierarchically structured indexed information retrieval system

A computer program product comprising computer readable instructions to cause a computer to execute said instructions, said instructions comprising instructions for implementing a retrieval object database for storing a plurality of retrieval object data and hierarchically-structured indexes constructed by a plurality of nodes and a plurality of leaves, wherein each of the plurality of nodes is connected with at least one node and/or at least one leave which are located one level of hierarchy below therefrom, and wherein each of the plurality of leaves has an index for each of the plurality of retrieval object data, said instructions further comprising instructions for implementing

• retrieval execution means for retrieving through the retrieval object database based on a retrieval condition input by a user so as to obtain retrieval result data, and
• narrowing-down execution means for obtaining question nodes corresponding to common nodes commonly connected with leaves pointing to the retrieval result data retrieved by the retrieval execution means within the hierarchically-structured indexes and for obtaining answer nodes that are located at a level of hierarchy just below a level of hierarchy to which each of the question nodes belongs, wherein narrowing-down factors are calculated with respect to the question nodes respectively so that the question nodes are presented for the user in a form that the user is capable of recognizing merits of the narrowing-down factors, whereby the narrowing-down execution means narrows down the retrieval result data on the basis of the answer node hat is selected by the user within the answer nodes to the question nodes selected by the user, wherein the instructions for implementing the narrowing-down execution means further comprises instructions for implementing
• first means, activated when leaves pointing to same retrieval result data exist in a level of hierarchy below a level of hierarchy to which the answer nodes belong, for newly obtaining nodes belonging to the same level of hierarchy of the answer nodes as new question nodes and for newly obtaining nodes located at a level of hierarchy just below the level of hierarchy of the new question nodes as new answer nodes, and
• second means, activated when leaves pointing to retrieval result data related to the new question nodes belong to a same level of hierarchy and when a level of hierarchy of the new question nodes is one level of hierarchy above the level of hierarchy of the leaves or is identical the level of hierarchy of the leaves, for disallowing utilization of the new question nodes.

An information retrieval system comprising:

• a retrieval object database for storing a plurality of retrieval object data;
• retrieval execution means for retrieving through the retrieval object database on the basis of a retrieval condition input by a user so as to obtain retrieval result data;
• storage means for storing hierarchically-structured indexes having nodes and leaves which are arranged in a tree structure, wherein each of the leaves has an index for the retrieval object data;
• question node means for obtaining question nodes corresponding to common nodes commonly connected with leaves pointing to the retrieval result data within the hierarchically-structured indexes;
• answer node means for obtaining answer nodes that are located below a level of hierarchy of each of the question nodes;
• occurrence probability calculation means for calculating occurrence probabilities each representing occurrence of prescribed retrieval object data within the retrieval result data;
• presentation means for presenting a user with the question nodes in an order determined by the occurrence probabilities;
• and
• narrowing means for narrowing down the retrieval result data to match with at least one answer node selected by the user, which is provided for at least one question node selected by the user.