CONTENT ACQUIRING DEVICE, METHOD, AND SYSTEM USING VALID TERMS TO KEEP A CACHE UP-TO-DATE

To provide a content acquiring device, a content acquiring method, a content server and a content acquiring system which can minimize an acquisition request for content data and can acquire content data having a current version as much as possible. By using a validity term previously held by the content acquiring device or a validity term of the content added during content acquisition, it is previously decided in the device whether the content are to be updated or not, thereby transmitting an acquisition request to be an access to a content server for storing content data requested to be acquired through a network.