The delivery of multimedia content often needs the adaptation of the content in order to satisfy user constraints. With the Digital Item Adaptation part, the MPEG-21 standard already defines a useful frame-work to handle this task. However, when the functionality of adaptation is split over several services the central instantiation of a suitable service chain needs to tackle a complex multi-objective optimization problem. In this problem between content choice and possible adaptations the current preference model in the MPEG-7/21 standard still lacks expressiveness. In the course of this paper we demonstrate this shortcoming and how the integration of more powerful models can ease the instantiation problem. As a running example we use a typical media streaming application with Web services as basic modules. We will let a central coordinator instantiate a service composition by integrating all needed Web services to adapt the multimedia content in the best possible fashion.