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The Layered Multimedia Data Model (LMDM) aids in the specification of multimedia compositions by dividing the problem into smaller, more manageable pieces. In this paper we describe the lower two layers of the LMDM, the Data Definition Layer, which allows the specification of multimedia objects in a database, and the Data Manipulation Layer, which allows the specification of temporal structures built from those objects. Several examples demonstrate the advantages of the layered paradigm: simple specifications, and modular, reusable components.

This paper deals with I/O throughput maximization in a single processor/multidisk database system, by means of optimal allocation of entire relations (or other nonfragmented data objects) to disks. We examine the cases in which such allocation is beneficial, and present a mathematical formulation of the problem. This formulation is shown to be flexible enough to accommodate various objectives and constraints of a typical system design.>

A new multicopy algorithm is proposed; it has the potentially attractive property that much less space is required and equal performance is provided during normal operation. On the other hand, during failures the new algorithm offers lower performance than a conventional scheme. As such, this algorithm may be attractive in various multicopy environments, as well as in disaster recovery. The algorithm is presented and compared with various other multicopy and disaster recovery techniques.>