Information retrieval system, registration apparatus for indexes for information retrieval, information retrieval method and program

Abstract

An information retrieval system comprising: an information acquisition unit that acquires information as a subject of retrieval; a time information specifying unit that specifies time information owned by said information as the subject of retrieval; and an index updating unit that updates said index using the time information specified by said time information specifying unit; wherein said information retrieval system provides an information retrieving function of reproducing retrieved results at any time point by providing index for information retrieval with the time information and by using data of said index relevant to a reference point of retrieval identified at the time of retrieval.

What is claimed is: 
     
         1 . A method of updating an index, the method comprising:
 determining a first time range of an index;   determining a time interval at which data has been backed up to a back up storage device;   one of merging the index into a first index and splitting the index into a first plurality of indexes based on a comparison between the first time range and the determined time interval; and   registering data stored into the back up storage device in the first index or the first plurality of indexes.   
     
     
         2 . The method of  claim 1 , wherein the index is split into the first plurality of indexes in response to the first time range being greater than the determined time interval. 
     
     
         3 . The method of  claim 1 , wherein the index is merged into the first index in response to the determined interval being greater than the first time range. 
     
     
         4 . The method of  claim 1 , wherein a time range of first index or each of the first plurality of indexes is same as the determined time interval.