Authoring multimedia documents involves coordinating various types of media items in time and space. To be effective, authoring requires integration tools that are highly interactive. In addition, the notion of “time” must be made explicit and flexible so that users may define and manipulate the temporal behavior of documents directly and flexibly. The authors describe an interactive framework for multimedia authoring, which provides users with immediate feedback. It is based on the elastic time model, where the temporal behavior of multimedia documents can be handled explicitly yet flexibly. In its implementation (the Isis* authoring system), users directly manipulate time via timebox diagrams, and the system immediately checks the validity of each user interaction. The system also provides guidance for recovery in anomalous situations. Users can query various temporal properties of the document and use automatic scheduling mechanisms. These system support tools are based on a fast incremental algorithm. Through this approach, multimedia documents can be designed so that they are adaptable to the needs of different users and to changing environments.