Network system, network household appliance, content/metadata synchronous processing method, and computer program

A content/metadata synchronous processing method, implemented by one or more computers, comprising the steps of:

• generating, by the one or more computers functioning as an update notification message generator, for each of a plurality of services, an update notification message that stores update information of a content or metadata of the content, or a reference to the update information;
• setting, by the one or more computers functioning as a filter attribute setting unit, in the update notification message for each service delivered from the update notification message generator, a filter attribute for categorizing the message;
• accumulating, in an update notification message accumulation unit, the update notification message in which the filter attribute has been set;
• updating, using the update information, the content or the metadata in a local content/metadata storage unit in a home network appliance that stores a content or metadata of a specific service, by an update unit including an application corresponding to the specific service;
• managing in advance, by the one or more computers functioning as an update information provision unit, a correspondence between the application and the filter attribute, specifying, based on the filter attribute set in the update notification message acquired from the update notification message accumulation unit via a network and the correspondence, an application that provides the update information within the update notification message, and providing the update information by activating the application;
• generating, by the update notification message generator, as the update information, full-update information as a full-update content of the content or the metadata and differential-update information as an update content of only a differential update while periodically switching them, and setting, in the update notification message, attribute information that indicates an update method of the update information of each update notification message, and
• acquiring, by the update information provision unit, from the update notification message accumulation unit via the network, based on the attribute information set in the update notification message accumulated in the update notification message accumulation unit, the update notification message necessary for synchronizing the content or the metadata in the local content/metadata storage unit with the content or the metadata on a side of a provider of the service.