Patent ID: 7584184
Filing Date: 2009-09-01
Classification: G06F,Y10S

Abstract:
1. A system for searching keywords from texts, the system comprising: a first index storage unit storing a first index which designates a list of keywords contained in the texts from identification information of the respective texts, wherein the first index is generated in advance based on a plurality of texts stored in a text database, and the first index is stored in the first index storage unit prior to a search of the keywords; a second index storage unit for storing a second index which designates a list of texts containing the keywords from identification information of the respective keywords, in a way that the second index corresponds to a number of texts containing the respective keywords, wherein the second index is generated in advance based on the plurality of texts stored in the text database; an input unit a determination unit a search unit for searching for and outputting keywords which appear in texts satisfying the text search condition with higher frequency than a predetermined standard, by using the index which is determined to make the search faster and the search unit outputs the keywords to a user; a ratio calculation unit for calculating a condition fulfillment rate indicating an occupancy ratio of texts which satisfy the text search condition among all texts to be searched; a function calculation unit for approximately calculating, based on the condition fulfillment rate, probability distributions of probability variables indicating the number of texts which contain the respective keywords and which satisfy the text search condition, and for calculating, based on a calculated probability distribution, a function for a threshold for obtaining the sum of probabilities that the probability variables of the respective keywords are not less than the threshold, wherein the function for calculating the threshold is: a threshold calculation unit for calculating the threshold at which the calculated function is substantially the same as the standard number; a second search time calculation unit for calculating the number of texts containing the respective keywords contained in texts whose number is greater than the calculated threshold, based on the number of the texts stored in the second index storage unit, and for calculating a product of the calculated number of texts and predetermined access time, as an estimation of search time by the second index; and a first search time calculation unit for calculating a product of the number of texts which satisfy the text search condition among a plurality of the texts to be searched and the predetermined access time, as an estimation of search time by the first index, wherein the determination unit determines that a search by the second index is faster, conditional upon the estimation of search time calculated by the second search time calculation unit is smaller than the estimation of search time calculated by the first search time calculation unit.