4. A method implemented by an apparatus for updating a previously supplied electronic document based on XML, wherein said previously supplied electronic document describes programming information about a plurality of television broadcast programs scheduled for broadcast in a program broadcasting system, and the previously supplied electronic document is stored in a client of the program broadcasting system and has a hierarchical structure based on a prescribed syntax, the hierarchical structure including an upper fragment and a plurality of lower fragments located below the upper fragment in the hierarchical structure to describe, for each of the scheduled television broadcast programs, a program identifier, a title, broadcast information and corresponding program content information, the method comprising: requesting by the client an updated version of said previously supplied electronic document from a provider in the program broadcasting system; in response to the request, receiving from the provider at the client an update document for updating said previously supplied electronic document, said update document having a structure based on the prescribed syntax and including the upper fragment and an invalid element which indicates that one of the lower fragments of the previously supplied electronic document is invalid, wherein said invalid fragment is identified by the invalid element and is related to one of the television broadcast programs scheduled for broadcast in the program broadcasting system; and deleting said invalid fragment from the previously supplied electronic document as indicated by the invalid element at said client.
4. A method implemented by an apparatus for updating a previously supplied electronic document based on XML, wherein said previously supplied electronic document describes programming information about a plurality of television broadcast programs scheduled for broadcast in a program broadcasting system, and the previously supplied electronic document is stored in a client of the program broadcasting system and has a hierarchical structure based on a prescribed syntax, the hierarchical structure including an upper fragment and a plurality of lower fragments located below the upper fragment in the hierarchical structure to describe, for each of the scheduled television broadcast programs, a program identifier, a title, broadcast information and corresponding program content information, the method comprising: requesting by the client an updated version of said previously supplied electronic document from a provider in the program broadcasting system; in response to the request, receiving from the provider at the client an update document for updating said previously supplied electronic document, said update document having a structure based on the prescribed syntax and including the upper fragment and an invalid element which indicates that one of the lower fragments of the previously supplied electronic document is invalid, wherein said invalid fragment is identified by the invalid element and is related to one of the television broadcast programs scheduled for broadcast in the program broadcasting system; and deleting said invalid fragment from the previously supplied electronic document as indicated by the invalid element at said client. 7. The method of claim 4 , wherein said invalid fragment is indicated to be invalid by an invalid attribute.