Synchronized multimedia applications play an important role in a Digital Library environment, since they allow one to efficiently disseminate knowledge among differently skilled users through an approach which is more direct than the classic ‘ static’ documents. In this paper, we propose a new authoring approach based on an innovative presentation structure and a new class of content based constraints. Thanks to a flexible heuristic process, such fea tures allow the author to easily combine several multimedia objects into a multi-topic presentation, whose different contents can be freely chosen by end users according to their preferences or skills.