INFORMATION RETRIEVAL DEVICE, INFORMATION COMPRESSING METHOD FOR INFORMATION RETRIEVAL DEVICE, AND RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To suppress the capacity of an index file by compressing index information more efficiently and to enable high-speed retrieval using the index file. SOLUTION: When entries of index information are successively identical, this information compressing method deletes by an index information compression part 107 the entries except only one entry, puts (n) successive pieces of index information with the same document number in one group as to index information in the same character chain, and generates compressed index information having the document number compressed into one. When byte data of position numbers are not larger than a reference value (0×0f), the low-order four bits of each of the byte data of the position numbers are connected to generate compressed index information having the position number converted into 1-byte data.