The media on which authors should publish pedagogical documents become every day more numerous, complexifying the work of either content authors, graphics designer or webmasters. We propose an XML application for content authors, to help them structure their hypertext documents in factorizing their common structure in a class, and to free them from all the other aspects. They design both a structural model (a class), and a presentation model (using HTML, WML,…). Using these two models, our HDML engine automatically builds the projection function able to transform any actual document into (for example) well-formed web pages. HDML also offers inheritance capabilities among classes, which allows an editor responsible for a whole document set to define its global structure, and to adapt it according to the different document sections needs.