Retrieval schedules based on resource availability and flexible presentation specifications

A distributed multimedia document presentation involves retrieval of objects from one or more document servers and their presentation at the client system. The presentation of the multimedia objects has to be carried out in accordance with the specification of temporal relationships between the objects. The retrieval of multimedia objects from the document server(s) is influenced by factors such as temporal specification of objects presentations, through-put offered by the network service provider, and the buffer resources on the client system. Flexibility in the temporal specification of the multimedia document may help in deriving an object retrieval schedule that can handle variations in network throughput and buffer resource availability. In this paper, we develop techniques for deriving a flexible object retrieval schedule for a distributed multimedia document presentation. The schedule is based on flexible temporal specification of the multimedia document using the difference constraints approach. We show how the derived retrieval schedule can be validated and modified to ensure that it can work with the offered network throughput and the available buffer resources.