Do not change the DTD without notifying the author. 6.5 Provide the author with a summary of the document accessibility status on a configurable schedule. 6.6 Allow the author to perform element transformations. For example, to transform visually formatted elements to structure elements, or tables to lists. Allow the user to define transformations for imported documents that have presentation, rather than structural, markup.
Prompts are simple requests for information before a markup structure has been finalized.
Prompts are relatively unintrusive and address a problem before it has been committed. However, once the user has ignored the prompt, its message is unavailable. Alerts warn the author that there are problems that need to be addressed. The art of attracting users' attention is a tricky issue. The way users are alerted, prompted, or warned will influence their view of the tool and their opinion of accessible authoring.