Jan Gecsei

Distributed multimedia and QOS: a survey

Quality of service (QOS) is increasingly important for all components within distributed multimedia systems, as this survey reveals. We discuss the QOS parameters found in communication protocols, operating systems, multimedia databases and file servers, as well as those directly affecting the human user. >

Lattice model of browsable data spaces

Abstract This article describes a new approach to database access suitable for browsing. The underlying data model consists of a number of objects, easily described by a variable number of keywords (simple or qualified). Navigation is performed in terms of certain subsets of keywords and objects (called contexts), which are shown to form a lattice. The complexity of the lattice grows linearly with the number of objects (and not exponentially, as would be the case if all possible keyword subsets were used). The method is illustrated by several practical examples.

Adaptation in distributed multimedia systems

The real-time requirements of continuous media call for careful resource management in distributed multimedia systems. In complex and mobile systems, however, effective resource reservation becomes almost impossible. Recent research suggests adaptive applications as a complementary solution. This article reviews heterogeneous networks and the rationale behind adaptation, gives implementation examples, and discusses some outstanding research issues.

Simulation of MOS Circuits by Decision Diagrams

This paper describes a novel approach to switch-level simulation of MOS circuits. The circuit is first partitioned into connector-switch networks CSN [4]. Then each CSN is represented in terms of a decision diagram DD, which is particularly suitable for use in simulators. The advantages of DDs are that they are based on a solid theory and they permit fast evaluation of the networks response to any input vector. The CSNs are coupled through a 3-state automaton representing charge wells associated with transistor gates.

Determining hit ratios for multilevel hierarchies

The applicability of stack processing for evaluation of storage hierarchies has been limited to two-level systems and to a very special group of multilevel hierarchies. A generalization of stack processing, called joint stack processing, is introduced. This technique makes possible the efficient determination of hit ratios for a class of multilevel hierarchies—staging hierarchies. These hierarchies are rather realistic in the sense that they allow for multiple block sizes and multiple copies of data in the hierarchy. Properties of storage management schemes that lend themselves to joint stack processing are studied, and the notion of distributed hierarchy management is described and illustrated.

Structuring knowledge bases using automatic learning

The need to add an automatic learning phase to the construction process of a knowledge base is stressed. This work introduces a new technique based on machine learning methodologies which automatically creates a particular knowledge representation structure called knowledge space, from which common generalizations of knowledge objects may be efficiently inferred. Also introduced are some of the improved and added processing capabilities made possible by this structure.<<ETX>>

Services, frameworks, and paradigms for distributed multimedia applications

Distributed multimedia application development is supported by a growing number of services. While these pave the way for sophisticated multimedia support in distributed systems, using them involves interfacing inconsistent and swiftly evolving technologies. To alleviate this, the authors propose an encompassing framework that offers all services under a unifying hybrid object/hypermedia paradigm.

On distributed multimedia presentational applications: functional and computational architecture and QoS negotiation

Approaches to a functional and a computational architecture for distributed multimedia presentational applications are developed. These approaches are illustrated by a case study, a multimedia news-on-demand service. The concept of Quality of Service (QoS) parameters is seen to determine the new characteristics of distributed multimedia applications. Accordingly the computational architecture for distributed multimedia presentational applications is developed in a QoS driven way within the the framework of the Reference Model of Open Distributed Processing. The concept of QoS interfaces is introduced in order to handle the QoS negotiation in a general and generic way. Objects in a distributed multimedia application can negotiate their QoS parameters through these QoS interfaces. Using this approach, variants of QoS negotiation protocols are investigated.

Self-Adjusting Networks for VLSI Simulation

Magnitude networks [1l, [2] have been used as a theoretical base for switch-level simulation of MOS VLSI circuits. We address in this paper the particular problem of evaluating the influence of switches in unknown state on the steady-state response of the network. A two-pass procedure based on local controllers attached to such switches is described and a hardware implementation is proposed which models magnitude networks as self-adjusting combinational circuits.

A multiple-fault tolerant sorting network

Fault tolerance of balanced sorting networks (BSNs), which have the same performance bound as the Batcher efficient sorting networks, is discussed. Preliminary studies of fault tolerance in a BSN which demonstrated 1-fault tolerance with and without redundant comparators and external permuters and 2-fault tolerance requiring redundancy are reviewed. The present study further develops a k-fault-tolerant BSN design, where k>or=2 can be arbitrary in principle, even without redundancy. The performance analysis shows that the new designs achieve much higher probabilities of correct sorting in the presence of faulty comparators than the previously reported designs.<<ETX>>