Lehrgebiet Informationssysteme

We present our efforts on realizing transformation independence in open, extensible, and highly distributed multimedia (database) systems. Transformation independence is an abstraction concept which allows clients to request operations on media objects without knowledge of the actual physical media representation. Systems supporting transformation independence are expected to dynamically determine an optimal realization of such a request, depending on the actually available materialization, processing and communication resources, and other criteria (e. g., a cost limit). Besides a detailed discussion of general media data abstractions, we focus on the abstract data and processing model called VirtualMedia, which provides a transformation independence framework for multimedia processing. In particular, we describe how transformation requests are represented and processed, exploiting semantic equivalence relations on filter graphs and redundant materialization, finally yielding instantiable plans for materializing the requested media object(s) at the client.

Internal Report, April 2001, 24 pages.