Optimization of Adaptive Data - Flows for Competing MultimediaPresentational Database

The " Arbeitspapiere der GMD – GMD Technical Reports " primarily comprise preliminary publications, specific partial results and complementary material. In the interest of a subsequent final publication the " Arbeitspapiere/Technical Reports " should not be copied. Critical comments would be appreciated by the authors. No part of this publication may be reproduced or further processed in any form or by any means without the prior permission of GMD. All rights reserved. Abstract Database systems which support preorchestrated multimedia presentations must be able to adapt the resource demand of executing presentations. Such adaptations can be dictated by underlying resource management components. When resources are not reserved, such adaptations are necessary to overcome uctuating resource availability. Adaptations across components of presentations as well as across concurrent sessions have to be considered in the context of the individual needs of presentation providers and viewers. This paper describes the general concept of Reactive Playout Management (RPM) which provides an application-independent service for adaptive multimedia presentations. The PYLOT scheme (PlaYout Load OpTimization scheme) is proposed which enables RPM in best-eeort architectures. In particular, the global allocation routine of PYLOT is elaborated. This routine allocates load shares which sessions must give up or may add on according to replugable adjustment strategies. In an optional post-optimization step, the routine manipulates the load proportions such that minimal total adjustment costs and maximal total adjustment proot are achieved, respectively. This optimization is demonstrated by experimental results.