Patent ID: 7188104
Filing Date: 2007-03-06
Classification: G06F,Y10S

Abstract:
1. An apparatus for retrieving documents, comprising: a processor; a document dividing part configured to divide each document into character strings as index keys; an index table configured to maintain the index keys and document information relating to each index key; a query character string dividing part configured to divide a query character string into a plurality of index keys; a retrieval condition analyzing part configured to analyze a retrieval condition including the index keys divided from the query character string and to generate a retrieval condition tree where the index keys divided from the query character string are synthesized by at least one operator that retrieves an intermediate retrieval result including the document information from said index table; and a retrieval condition evaluating part configured to evaluate each intermediate retrieval result obtained by the retrieval condition tree, to determine a final retrieval result, and to retrieve documents of the final retrieval result, wherein: said document dividing part divides the document into index keys of n-character strings having n characters and rn-character strings having m characters where n is an integer greater than one and m is an integer less than n, and each of the rn-character strings includes a last character of the document, when at least two index keys are divided from the query character string by said query character string dividing part, said retrieval condition analyzing part includes: a first condition tree generating part generating a first condition tree synthesized by at least one AND set operator obtaining an AND set of a plurality of intermediate retrieval results based on said at least two index keys, and a second condition tree generating part selecting a minimum number of index keys, which cover a full length of the query character string, from said at least two index keys and generating a second condition tree synthesized by at least one distance operator indicating a distance between appearance positions of said at least two index keys, said retrieval condition analyzing part includes a document determining part obtaining candidate documents by executing the first condition tree and determining documents from the candidate documents by calculating the second condition tree, and said first condition tree generating part generates the first condition tree by index keys used in the second condition tree and other index keys positioned in the query character string before or after the index keys used in the second condition tree and indicating a least number of the documents including the other index keys.