δ-sets for optimized reactive adaptive playout management in distributed multimedia database systems

A novel database system service called a playout management service, which performs multimedia presentations was proposed by the authors recently [1st Int. Workshop on Multimedia Database Mgmt. Systems, pp. 38-47, 1995]. In distributed multimedia database systems without end-to-end guarantees, such a playout management service faces the potential problem that system performance can become insufficient when realizing a stored presentation. This problem can be overcome by making the playout management service reactive, such that it balances the amount of data to be fetched from a remote multimedia database with the system performance that is available. For the users, this means that a running presentation is adapted by the playout management service. In this paper, we propose the concept of a δ-set to adapt the execution of arbitrary multimedia presentations in an optimized way. We present a heuristic scheme to identify the most adequate δ-set with respect to (1) the actual system state, (2) the user preferences, and (3) the specific properties of multimedia presentations