35. The method of claim 34 , wherein said invalid element is defined in said prescribed syntax.
34. A method implemented by an apparatus for replying to a request for updating a previously supplied electronic document related to a schedule of broadcasting a plurality of television broadcast programs in a program broadcast system, wherein said 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: supplying said client with an update document from a provider of the program broadcasting system, the update document having a structure based on the prescribed syntax and including the upper fragment and an invalid element to delete a first lower fragment of said previously supplied electronic document at the client, wherein said invalid element indicates that said first lower fragment is invalid and should be deleted from the previously supplied electronic document, wherein the invalid first lower fragment is related to one of the scheduled television broadcast programs.