A multimedia presentation refers to the presentation of multimedia data using output devices such as monitors for text and video, and speakers for audio. Each presentation consists of multimedia segments which are obtained from a multimedia data model. In this paper, we propose to express semantic coherency of a multimedia presentation in terms of presentation inclusion and exclusion constraints that are incorporated into the multimedia data model. Thus, when a user specifies a set of segments for a presentation, the DBMS adds segments into and/or deletes segments from the set in order to satisfy the inclusion and exclusion constraints. To automate the assembly of a presentation with concurrent presentation streams, we also propose presentation organization constraints that are incorporated into the multimedia data model, independent of any presentation. We give two algorithms for automated presentation assembly and discuss their complexity. We discuss the satisfiability of inclusion and exclusion constraints when negation is allowed. And, we briefly describe a prototype system that is being developed for automated presentation assembly.