The creation of a multimedia presentation is a non-trivial task. It involves skills that are not readily available to users and it requires support not generally available from authoring software. In order to understand the basic problems of multimedia authoring, this article considers the requirements for defining interactive, dynamic presentations. When contrasted against the facilities available in current-generation commercial authoring systems, we can see that their focus is often on low-level details rather than high-level structure. The prospects for future editing systems are somewhat brighter: support for high level editing can be provided. As an example, we describe the CMIFed authoring environment; CMIFed not only supports author...