29. The method of claim 26 , wherein the version identifier is expressed in the form of YYYYMMDD, wherein YYYY, MM, and DD are numerical expressions of year, month, and day, respectively.
26. A method implemented by a provider in a broadcasting system for updating metadata related to multimedia program content scheduled for broadcast in the broadcasting system, the method comprising: receiving by the provider a request from a client device in the broadcasting system for an updated version of a lower fragment in the metadata related to the scheduled multimedia program content, the client device storing an earlier version of the metadata, wherein the metadata has a hierarchical structure based on a prescribed syntax and the hierarchical structure includes an upper fragment above the lower fragment, and wherein the earlier version is identified by a version identifier; and in response to the request, sending from the provider to the client device an update document having a structure based on the prescribed syntax, the update document including the upper fragment and an invalid element, wherein the invalid element specifies that information in the lower fragment of the earlier version of the metadata is invalid.