Wolfgang Theilmann

Dynamic distance maps of the Internet

There is an increasing number of Internet applications that attempt to optimize their network communication by considering the network distance across which data is transferred. Such applications range from replication management to mobile agent applications. One major problem of these applications is to efficiently acquire distance information for large computer networks. This paper presents an approach to creating a global view on the Internet, a so-called network distance map, which realizes a hierarchical decomposition of the network into regions and which allows us to estimate the network distance between any two hosts. This view is not only a single snapshot but is dynamically adapted to the continuously changing network conditions. The main idea is to use a certain set of hosts for performing distance measurements and to use the so-gained information for estimating the distance between arbitrary hosts. A hierarchical clustering provides the notion of regions and allows us to coordinate the measurements in such a way that the resulting network load is minimized. An experimental evaluation on the basis of 119 globally distributed measurement servers shows that already a small number of measurement servers allows us to construct fairly accurate distance maps at low cost.

Optimizing the dissemination of mobile agents for distributed information filtering

Reduced communication costs can motivate programmers to use mobile agent technology. The authors analyze the use of mobile agents for filtering distributed information resources and present an approach for coordinating mobile agent dissemination that minimizes communication costs.

Domain Experts for Information Retrieval in the World Wide Web

The World Wide Web is the largest collection of documents that ever existed. Users of this information space do need tools for simple and powerful retrieval of the information they are interested in. But the existing search tools have turned out to be insufficient. They either do not scale with the large amount of available data or their results are of low quality.

Efficient dissemination of mobile agents

An often claimed benefit of mobile agent technology is that it reduces communication cost, but there is hardly any scenario in which this advantage has been proven or quantified on an Internet scale. One important reason for this lack of quantification is that agent systems do not have global knowledge about the quality of network connections between arbitrary agent platforms and data servers. We present an approach for representing a network in a way that allows to derive approximately the quality of network connections between agent platforms and data servers. By using this representation we provide an algorithm which computes a schedule for the efficient dissemination of a mobile agent. The experimental validation of our approach shows that communication cost can be reduced by more than 50 percent in many situations.

Workshop on models for non-functional properties of component-based software – nfc

Developing reliable software is a complex, daunting, and error-prone task. Many researchers are interested in improving support for developers creating such software. Component-based software engineering has emerged as an important paradigm for handling complexity. In addition, using models to raise the level of abstraction when reasoning about systems, is another technique to lower complexity. The goal of the NfC series of workshops is to look at issues related to the integration of non-functional property expression, evaluation, and prediction in the context of component-based software engineering and find the best techniques to deal with non-functional properties in a model based approach. Approaches need to include semantic issues, questions of modeling language definition, and also support for automation, such as analysis algorithms, MDA-based approaches, and tool-support for refinement steps. Since models are only really meaningful if used in the context of a software development process, the workshop also welcomes work in this area. The aim of the 2005 NfC workshop was to bring together practitioners and academics that are currently working with these topics and highlight the ongoing solutions and problems still remaining. The 2005 NfC workshop was organized as two half-day sessions: The morning session was dedicated to presentations and discussion of papers, followed in the afternoon by working sessions. The topics of the working sessions were derived from the morning discussions, and from topics discussed in the 2004 NfC workshop.

Effiziente Informationssuche im Internet mit Hilfe mobiler Programme

Zusammenfassung. Die Bereitstellung eines präzisen, effizienten und möglichst vollständigen Zugriffs auf aktuelle Informationen im Internet ist eine grundlegende Voraussetzung für die Weiterentwicklung des elektronischen Handels. Dieser Beitrag zeigt, wie themenspezifische Suchwerkzeuge mit Hilfe mobiler Programme eine solche Bereitstellung leisten können. Der vorgestellte Ansatz wird durch messdaten-basierte Simulationen sowie anhand einer Fallstudie evaluiert.Abstract. The precise, efficient and almost comprehensive access to information currently available on the Internet is a fundamental prerequisite for the further development of electronic commerce. This paper reports how subject specific search tools that use mobile code technology can realize such an access. The approach is evaluated with trace-driven simulations and with a case study for the domain of scientific articles.