A multimedia document consists of different types of media objects that are to be presented at different instants of time and for different durations. The media objects may be stored in computer systems connected by a network, thereby rendering the document distributed. The authors may wish to collaborate in a distributed manner to edit a multimedia document. Hence, an authoring system needs to identify a retrieval schedule that describes the time instants at which the objects have to be retrieved as well as the logical paths to be followed by the objects. In this paper, we consider a collaborative multimetia document authoring system with the above mentioned features. We propose a difference constraints based temporal specification for the multimedia document. This approach allows us to generate flexible schedules for retrieving objects over the computer network. This flexible retrieval schedule can handle variations in system parameters such as available network throughput and buffer resources
