Lehrgebiet Informationssysteme

In this report, we give an overview of the SFB 501 approach on developing abstractions and concepts needed to achieve the long-term objective of realizing a genuine universal media server. Such a media server is supposed to supplement repositories of any kind (e. g., digital libraries) by providing a high-level interface that allows applications to access and process media data over a network (including the world-wide web).

We focus primarily on the problem of optimally processing raw media data at the server. The traditional data independence abstraction, which is to be realized by a universal media server, is known to be impeding the processing of media data with optimal performance and/or quality. However, instead of abandoning data independence (which is most usual for media servers today), we propose an enhancement that is particularly tailored to the characteristics of networked media data processing: transformation independence. Conceptually, transformation independence can be supported by introducing a virtual media object layer at the server.

The VirtualMedia concept accordingly presented in this paper takes advantage of the common filter graph model to introduce a logical representation of such virtual media objects. Principles and rules for deriving optimal plans to materialize virtual media objects are also considered. We compare our approach with other realizations of media-ADTs (particularly the E-ADT approach) and, finally, draw some conclusions regarding urging problems which have to be addressed in the future.

Keywords

Media Server, Media-specific Abstract Data Types, Data Independence

SFB-Report 03/2000, SFB 501, University of Kaiserslautern, Feb. 2000, 19 pages.