Patent ID: 9600565
Date: 2017-03-21
CPC Classifications: G06F

Claim:
1. In a taxonomy having a tag with respect to search subject data, an index creation device configured to create an inverted list used for taking out a set of search subject data which can be reached from each node in said taxonomy, wherein a list of integer values in an inverted list of said each node is divided into two or more blocks, and a differential value between an integer value and an integer value directly before said integer value in said block is converted into a bit string of a variable length integer code, and said index creation device, realized by a computer, comprises: a processor configured to execute instructions to implement: an ancestor node determination part configured to select one ancestor node that is a higher node of said node for every node in said taxonomy, and generate data for ancestor reference indicating selected said ancestor node; an ancestor node search part configured to generate an ancestor node list indicating one or more ancestor nodes of a tag in said taxonomy based on said data for ancestor reference; and an ancestor number converting part configured to, upon receiving an identifier of search subject data, with respect to the highest node among each said node in said ancestor node list, adds said identifier as an element of a corresponding inverted list, and with respect to a node other than said highest node, as an element of a corresponding inverted list, in place of said identifier, adds an integer value indicating a position in an inverted list corresponding to a node that is higher by one than said node, wherein said ancestor node determination part, upon receiving a frequency distribution indicating whether each node in said taxonomy has or may have to what extent of a frequency within a prescribed data set, for every node in said taxonomy, based on a frequency corresponding to each ancestor node of said node, calculates a data length of a corresponding inverted list in the case of selecting said each ancestor node, and among said each ancestor node, selects preferentially said ancestor node where said data length is small and said ancestor node of a higher order in said taxonomy.