20. A method implemented by a client in a broadcasting system for managing metadata for multimedia program content scheduled for broadcast in the broadcasting system, the method comprising: receiving in the client from a provider in the broadcasting system a first version of an electronic document containing metadata related to the scheduled multimedia program content, wherein the electronic document has a hierarchical structure based on a prescribed syntax and the hierarchical structure includes an upper fragment located above a first version of a lower fragment, and wherein the first version of the lower fragment is identified by a version identifier; storing the first version of the lower fragment in a local data structure of the client, wherein the local data structure is based on the prescribed syntax and corresponds to the electronic document; requesting an update for the previously received lower fragment in the client; and in response to the request, receiving in the client 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 the version identifier of the earlier version of the lower fragment.
20. A method implemented by a client in a broadcasting system for managing metadata for multimedia program content scheduled for broadcast in the broadcasting system, the method comprising: receiving in the client from a provider in the broadcasting system a first version of an electronic document containing metadata related to the scheduled multimedia program content, wherein the electronic document has a hierarchical structure based on a prescribed syntax and the hierarchical structure includes an upper fragment located above a first version of a lower fragment, and wherein the first version of the lower fragment is identified by a version identifier; storing the first version of the lower fragment in a local data structure of the client, wherein the local data structure is based on the prescribed syntax and corresponds to the electronic document; requesting an update for the previously received lower fragment in the client; and in response to the request, receiving in the client 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 the version identifier of the earlier version of the lower fragment. 22. The method of claim 20 , wherein the version identifier is a numerical representation of a calendar date on which the earlier version was created.