05 Fakultät Informatik, Elektrotechnik und Informationstechnik

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Author: search.filters.author.Baumann, JoachimEnd date: 2009

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Now showing 1 - 9 of 9
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    ATOMAS : a transaction-oriented open multi agent system; final report
    (1998) Straßer, Markus; Baumann, Joachim; Hohl, Fritz; Schwehm, Markus; Rothermel, Kurt
    The electronic marketplace of the future will consist of a large number of services located on an open, distributed and heterogeneous platform, which will be used by an even larger number of clients. Mobile Agent Systems are considered to be a precondition for the evolution of such an electronic market. They can provide a flexible infrastructure for this market, i.e. for the installation of new services by service agents as well as for the utilization of these services by client agents. Mobile Agent Systems basically consist of a number of locations and agents. Locations are (logical) abstractions for (physical) hosts in a computer network. The network of locations serves as a unique and homogeneous platform, while the underlying network of hosts may be heterogeneous and widely distributed. Locations therefore have to guarantee independence from the underlying hard- and software. To make the Mobile Agent System an open platform, the system furthermore has to guarantee security of hosts against malicious attacks.
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    An agent based framework for the transparent distribution of computations
    (1999) Straßer, Markus; Baumann, Joachim; Schwehm, Markus
    A mobile agent based framework for the transparent distribution and concurrent execution of computations is presented. The framework uses design patterns like the master-slave, abstract factory or the strategy pattern. The architecture of the framework is built on top of a mobile agent system. A performance model allows to identify performance bottlenecks and unbalanced situations within the framework. The framework has been implemented and tested on top of the mobile agent system Mole.
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    The shadow approach : an orphan detection protocol for mobile agents
    (1998) Baumann, Joachim; Rothermel, Kurt
    Orphan detection in distributed systems is a well researched field for which many solutions exist. These solutions exploit well defined parent-child relationships given in distributed systems. But they are not applicable in mobile agent systems, since no similar natural relationship between agents exist. Thus new protocols have to be developed. In this paper one such protocol for controlling mobile mobile agents and for orphan detection is presented. The shadow' approach presented in this paper uses the idea of a placeholder (shadow) which is assigned by the agent system to each new agent. This defines an artificial relationship between agents and shadow. The shadow records the location of all dependent agents. Removing the root shadow implies that all dependent agents are declared orphan and are eventually terminated. We introduce agent proxies that create a path from shadow to every agent. In an extension of the basic protocol we additionally allow the shadow to be mobile. The shadow approach can be used for termination of groups of agents even if the exact location of each single agent is not known.
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    AIDA II - Abschlußbericht
    (2000) Hohl, Fritz; Baumann, Joachim; Rothermel, Kurt; Schwehm, Markus; Theilmann, Wolfgang
    In diesem Bericht geht es um die Zusammenfassung der Erkenntnisse, die im Verlauf der zweiten Phase des AIDA-Projektes von März 1998 bis Februar 2000 gewonnen wurden. AIDA ist ein Projekt, das von der Deutschen Forschungsgemeinschaft (DFG) finanziert wird. Das Thema dieses Projektes sind Systemmechanismen zur Unterstützung mobiler Agenten, also Einheiten, die aus Code, Daten und Zustand bestehen und sich selbstständig in einem Netzwerk bewegen können. Die Ziele von AIDA II waren die Erarbeitung des Themenbereichs Sicherheit in Mobile-Agenten-Systemen mit Schwerpunkt auf der Sicherheit mobiler Agenten gegenüber böswilligen Hosts, die Implementierung von Terminierungsprotokollen und Waisenerkennungsmechanismen, Abrechnungsmechanismen und schließlich Mechanismen zur Strukturunterstützung für Agentenanwendungen.
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    A protocol for orphan detection and termination in mobile agent systems
    (1997) Baumann, Joachim
    Orphan detection and termination in distributed systems is a well researched field for which many solutions exist. These solutions exploit well defined parent-child relationships given in distributed systems. But they are not applicable in mobile agent systems, since no similar natural relationship between agents exist. Thus new protocols have to be developed. In this paper one such protocol for orphan detection and agent termination is presented. First we present two approaches, the energy concept and the path concept. The energy concept is a passive termination protocol, and the path concept is a protocol for finding agents, that can be used to implement active termination. The energy' approach is based on the idea that an agent is provided with a limited amount of energy, which can be spent in exchange for the resources used by the agent. From time to time the agent has to request additional energy from its creator. The agent is terminated as soon as the energy falls to 0. This approach to agent termination implicitly implements orphan detection, i.e. if the creator has terminated, the dependent agents are killed as soon as they have no energy left. The path' approach uses a chain of proxies. As soon as an agent leaves a location, a proxy is created that points to the new location. By following the chain of proxies, the path, one can find any agent, and consequently terminate it. Both approaches have disadvantages. By merging them on different levels we create a protocol that combines the advantages of both approaches, and at the same time minimizes the disadvantages. The shadow' approach uses the idea of a placeholder (shadow) which is assigned by the agent system to each new agent. The shadow records the location of all dependent agents. Removing the root shadow implies that all dependent shadows and agents are terminated recursively.
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    Efficient algorithms to find optimal agent migration strategies
    (1998) Iqbal, Ashraf; Baumann, Joachim; Straßer, Markus
    Abstract Mobile agent technology has received a rapidly growing attention over the last few years. A number of mobile agent systems are under development in academic as well as industrial environments, there are already various moves to popularize and standardize mobile agent facilities and architectures. It has been argued that mobile agents provide certain advantages as compared to traditional approaches in terms of providing facilities like software-distribution on demand at reduced communication costs, better support for asynchronous tasks, and scalibility due to dynamic deployment which is based on a taxonomy of mobility. The employment of mobile agents has been particularly attractive in applications like information retrieval in widely distributed heterogeneous environments, network management, electronic commerce and in mobile computing. Inspite of all this growing interest and efforts the agent technology is in a fairly early stage and a number of technical problems should be solved in order to make this new technology a commercial success. These open problems include mechenisms for agent security, control structures, transactional support, and design of communication models. In this paper we extend previous research conducted on mobile agents regarding their communication performance models. It has been indicated that the optimal performance of an agent is achieved by a critical sequence of mixed remote procedure calls and agent migration. We provide here exact algorithms to solve various variants of this problem under certain restrictions on the sequence of interactions of the mobile agents.
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    A comparison of mechanisms for locating mobile agents
    (1999) Baumann, Joachim
    In this paper we present different possible approaches for locating mobile agents and introduce a classification for them. We will use this classification to categorize mechanisms proposed in standards and implemented in mobile agent systems. Then we assess the different mechanisms regarding their fault tolerance, their message complexity and the migration delay they induce. We conclude by combining the different assessments to allow a comparison of all mechanisms.
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    AIDA I - Abschlußbericht
    (1998) Hohl, Fritz; Baumann, Joachim; Rothermel, Kurt; Schwehm, Markus; Straßer, Markus
    In diesem Bericht geht es um die Zusammenfassung der Erkenntnisse, die im Verlauf der ersten Phase des AIDA-Projektes bis September 1997 gewonnen wurden. AIDA ist ein Projekt, das von der Deutschen Forschungsgemeinschaft (DFG) finanziert wird. Das Thema dieses Projektes sind mobile Agenten, also Einheiten, die aus Code, Daten und Zustand bestehen und sich selbständig in einem Netzwerk bewegen können. Das Ziel von AIDA I war es, auf der Grundlage eines allgemeinen Verarbeitungsmodells flexible Systemmechanismen für verteilte, agentenbasierte Systeme zu entwickeln.
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    Control algorithms for mobile agents
    (1999) Baumann, Joachim; Rothermel, Kurt (Prof. Dr. rer. nat.)
    In dieser Abhandlung werden verschiedene Kontrollmechanismen für mobile Agenten vorgeschlagen. Kontrollmechanismen werden sowohl für das Auffinden als auch für die Terminierung und Waisenerkennung von mobilen Agenten verwendet. Wir beginnen mit der Diskussion von Kontrollmechanismen, die spezifisch für den Einsatz im Bereich der mobilen Agenten entworfen wurden und dementsprechend die Eigentümlichkeiten des Paradigmas in Betracht ziehen. Das Energiekonzept wird präsentiert, das Waisenerkennung für mobile Agenten unterstützt. Dann wird das Pfadkonzept diskutiert, das in einer Variante im Bereich der verteilten Systeme verwendet wird, um mobile Objekte zu finden. Das dritte vorgestellte Konzept ist das Schattenkonzept. Dies Konzept unterstützt Auffinden, Terminierung und Waisenerkennung für mobile Agenten. Es erreicht dies durch eine Kombination von Energie- und Pfadkonzept auf eine Weise, die die Autonomie der Agenten wenig beschränkt, geringe Kommunikationskosten nach sich zieht, und überdies hervorragende Fehlertoleranzeigenschaften aufweist. Für jedes der Konzepte wird die Fehlertoleranz und die Nachrichtenkomplexität diskutiert. Im Bereich der verteilten Algorithmen sind Mechanismen entwickelt worden, die vergleichbare Probleme lösen. Es wurde gezeigt, daß zwei bedeutende Klassen, Terminierungsalgorithmen und Algorithmen für verteilte Garbage Collection, äquivalent sind. Transformationen, die die Konvertierung von Algorithmen einer der beiden Klassen in Kontrollalgorithmen für mobile Agenten erlauben würden, könnten den Zugriff auf eine große Menge von Algorithmen für die Kontrolle von mobilen Agenten ermöglichen. Allerdings sind die Fehlermodelle der verschiedenen Bereiche so grundsätzlich unterschiedlich, daß die direkte Verwendung unmöglich ist. Wir zeigen deshalb mit Hilfe von Transformationen, daß alle Prinzipien von transformierten Algorithmen auch in den Algorithmen zu finden sind, die explizit für mobile Agenten entworfen wurden.