1. A method implemented by an apparatus for supplying electronic documents based on XML, the method comprising: supplying from a provider of a program broadcasting system to a client in the program providing system an electronic document that uses XML to describe programming information about a plurality of television broadcast programs scheduled for broadcast in the program broadcasting system, the electronic document having 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; and supplying from the provider to the client an update document to update the previously supplied electronic document, the update document having a structure based on the prescribed syntax and including the upper fragment and an invalid element to identify an invalid fragment as one of the lower fragments in the hierarchical structure, wherein the invalid fragment is related to one of the television broadcast programs described in the previously supplied electronic document, and wherein the update document indicates deletion of said invalid fragment from the electronic document according to the invalid element.