DIGITAL INFORMATION DEGRADATION METHOD, DEVICE AND PROGRAM

摘要

PROBLEM TO BE SOLVED: To provide a method, a device and a program for reducing the information quantity by determining beforehand a hold period of digital information by a distributor or a user and degrading the digital information having a reduced utility value following aging, in order to solve the problems that the digital information characterized by having no aging consumes continuously a computer resource and becomes difficult to be managed as long as being explicitly deleted by the user, and that the information elapsing as long as a fixed period can not be restored after being deleted. SOLUTION: The digital information is allowed to have a period (service life) for holding a compression ratio or the information quantity. Old information is degraded corresponding to significance of the digital information following the lapse of time. The degradation means deletion of a prescribed item of the digital information or compression of the digital information by a prescribed system. The information quantity is reduced by degrading the information.