Peter Sturm

Introducing application-level replication and naming into today's Web

Abstract Because of its enormous success, the World-Wide Web created many problems within the Internet, most of them due to its huge bandwidth requirements. Additional applications using the Webs infrastructure for distributed computing (see, e.g., [5]), even further increase network load. In this paper, we are presenting a comprehensive application-level approach to solving the Web-induced bandwidth and latency problems within the Internet while staying fully compatible with the current mechanisms of the World-Wide Web. Our approach is based on automated replication schemes and complementary name services. In this paper, we are going to introduce these two concepts, and explain the many advantages they bring not only to every Web user but also to the various network and service providers currently struggling to keep up with rising user demands. In addition to an abstract presentation of this approach, we are also highlighting the concepts of our freely available implementation.

WebMake: integrating distributed software development in a structure-enhanced Web

Abstract In this paper, a technique for structuring large amounts of interdependent data is presented. This approach which facilitates graph-based hierarchical structuring and allows for the defintion of arbitrary views on graph structures can be applied to a broad range of very different application areas. Based on this concept we implemented a distributed software development environment supporting cooperative work on top of the World-Wide Web. In general, the approach is intended to serve as a basis for decentralized efforts to tame the immense and hardly manageable collection of data accessible in the Web.

A Java-Based Uniform Workbench for Simulating and Executing Distributed Mobile Applications

Spontaneous multihop networks with high device mobility and frequent fluctuations are interesting platforms for future distributed applications. Because of the large number of mobile devices required for any detailed analysis, it is nearly impossible to deploy prototype applications yet. In this paper, a comprehensive approach is presented which supports experiments ranging from pure simulation of several thousand mobile devices over hybrid scenarios with interaction among simulated as well as real life devices up to dedicated field trials. Part of this paper are also conclusions drawn from experiences with a first prototype version of a self-organized auction system for ad-hoc networks.

Architecture-Centric Software Development Based on Extended Design Spaces

The realization of software projects can be significantly eased by extending the focus of reuse to architectural aspects instead of concentrating on separate software elements. Yet in any case, operational techniques are required to support the retrieval and selection of reusable items. To this end, we extend on the concept of design spaces which allows to describe the relevant properties of software elements in a semi-formal way. Moreover, we show how the concept of extended design spaces can be deployed in tools supporting component-and framework-based software development.

Epidemic Self-Synchronization in Complex Networks of Kuramoto Oscillators

In this article, we present and evaluate an epidemic scheme for the synchronization of coupled Kuramoto oscillators in communication networks. It addresses the problem of efficiently providing globally synchronous time epochs in complex, dynamic Peer-to-Peer network topologies. Rather than the usual model of continuously coupled nodes, a discretized version with sporadic message-based couplings to nearest neighbors is considered. This article empirically studies the emergence of coherent oscillator states for different network topologies, coupling functions, and sporadic coupling intensities. It further investigates the protocols minimum bandwidth requirements in small-world network topologies. Synchronization resilience under the effect of random perturbations is studied for two coupling variations. Finally, the potential utilization of the scheme for a local inference of global network topology characteristics is discussed.

Elastic Consistency in Decentralized Distributed Virtual Environments

Distributed virtual environments like online games or 3D virtual worlds have become very popular in the last few years and a more substantial surge in popularity and use is expected. Because of the huge number of users, such environments will undergo a change of infrastructure from a centralized to a decentralized one, making higher demands on consistency issues. This paper addresses consistency problems which may occur in distributed virtual environments and introduces the elastic consistency model to tackle these problems. According to elastic consistency, different consistency levels setting up a trade-off between consistency and responsiveness of the environment should be introduced in order to provide an efficient way of interaction on a global scale.

HyperVerse: simulation and testbed reconciled

When dealing with dynamic large-scale topologies such as those underlying Peer-to-Peer (P2P) Distributed Virtual Environments (DVEs), one inescapably reaches the point where either: a) simulations lack human behaviour and assessment or where b) practical experiments on a small scale do not yield significant results. The restrictions resulting from the separation of simulation and testbed environments hinder a comprehensive assessment and efficient development of adaptive algorithms and techniques for DVEs as they are investigated in our HyperVerse research project. In this paper, we present a hybrid evaluation system designed to combine the advantages of simulations and testbeds. The proposed infrastructure exhibits great flexibility particularly alluring in view of the multitude of potential research in the context of DVEs.

Marketplaces as Communication Patterns in Mobile Ad-Hoc Networks*

This paper proposes a novel communication pattern for mobile multihop ad-hoc networks which is based on a marketplace metaphor. In order to substantially increase the probability that negotiating peers sucessfully reach an agreement, communication is focused on a static geographic area, called the marketplace. Users are not constrained to be at the marketplace physically, but are allowed to utilize other ones mobile devices located at the marketplace to let a software agent or a service installed on each device negotiate with others on their behalf. The forwarding and negotiation protocols needed to implement the marketplace solution are described in this work. Additionally, a prototypical implementation of the protocols is evaluated in a simulation environment. Since simulation results strongly depend on the mobility model, three realistic models based on an extension of the random way-point model are used. Their movement patterns are resulting from persons on a music festival, a university campus, and an exhibition.

Booster: A WWW-based prototype of the global software highway

A framework for globally distributed software development and management environments, which we call Booster is presented. Additionally, the first experiences with WebMake, an application developed to serve as an experimental platform for a software development environment based on the World Wide Web and the Booster framework is introduced. Booster encompasses the basic building blocks and mechanisms necessary to support a truly cooperative distributed software development from the very beginning to the last steps in a software life cycle. It is thus a precursor of the Global Software Highway, in which providers and users can meet for the development, management, exchange and usage of all kind of software.<<ETX>>

From Distributed Systems to Ubiquitous Computing

We summarize trends in communication paradigms for networked systems, mention well-established as well as innovative software infrastructures for distributed systems (such as COM+, CORBA, .NET and Jini), and give an overview of application domains such as grid computing, peer-to-peer computing, and mobile agents. We then discuss issues in spontaneous networking, and we explain the vision of Ubiquitous Computing and its intriguing prospects.