05 Fakultät Informatik, Elektrotechnik und Informationstechnik

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/6

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Institute: search.filters.UBSInstitut.Institut für Parallele und Verteilte SystemeStart date: 2004End date: 2004

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    ItemOpen Access
    Event management for mobile users
    (2004) Bauer, Martin
    This technical report presents the results of the project "Event Management for Mobile Users", a research cooperation between Universität Stuttgart and Microsoft. In Vienna, Microsoft chief executive Bill Gates recently expressed his vision of a seamless interaction of different computing devices, from PC to mobile phone, that proactively support the users wherever they go. Among other things, he said: "For example, if you want to be notified about something that's changing, that's important to you, software should know which device you have with you and should know what you're doing, know the context to understand if interrupting you with this new information is appropriate or not." (Bill Gates, January 28, 2004, [Los Angeles Times 2004]) This project may present one step towards realizing his vision. It is about event support for mobile users. Depending on their current context, they want to be informed about events that occur in the world around them - the physical as well as the virtual world of digital information systems. So, to optimally support its users, future generations of web services will need information about the real-world context of the user, especially their spatial context. This project was carried out in close cooperation with the Nexus project at Universität Stuttgart, whose goal is to support mobile context-aware applications based on a distributed spatial world model. Events of special interest in this context are spatial events, i.e. events that occur when a certain spatial constellation of objects is reached, e.g. when two people meet or when a customer enters a shopping mall. As the underlying world model is distributed, the events have to be observed on a distributed model. The number of potential spatial events is not restricted, e.g. the event that a user enters an area could be of interest for arbitrary areas. Also, as the spatial world model is distributed over many servers, a local observation is no longer sufficient. Therefore, the well-known publish-subscribe paradigm, in which the observation occurs implicitly within local observers, has to be extended. We propose an observation-notification paradigm, in which the observation of events has to be explicitly initiated by interested clients. The event service that conforms to the new paradigm consists of two components: an observation service, which observes events through a distributed model, and a notification service, which efficiently delivers event notifications. This paradigm applies to all scenarios in which the data needed for the observation of events is distributed over multiple sources. The user wants the specification of events to be as simple and easy as possible. He only wants to specify what event is to be observed, not how the observation of the event is realized. Therefore the distribution aspects should be transparent to the user. However, these aspects have a strong influence on the accuracy of the model and thereby directly affect the accuracy of event observation. We propose that the user specifies an event as a predicate, which becomes true when the event has occurred, plus a threshold probability. If the probability that the event has occurred is above the threshold probability, the event is considered to have occurred and an event notification is sent. The above sketched solution requires calculating the probability with which an event has occurred. We first show which parameters influence the accuracy of the data. We then present update protocols that guarantee a certain accuracy of data in the observer model, i.e. the model where the event is actually observed. Finally we show, how the occurrence probability can be calculated. Based on the identified parameters, the placement of the observation in the system can also be optimized with regard to the accuracy of the data. We have implemented the event service and integrated it into the Nexus platform. As the Nexus platform is intended as an open platform with possibly world-wide scale, scalability, efficiency and interoperability have been important requirements for the design of the components. To support interoperability, we have built on standard technologies like XML, HTTP and SOAP. The evaluation of the event service within the Nexus context shows the feasibility of the approach. We were able to show that the event service performs adequately in certain example scenarios. Experiments with a large-scale scenario are the next steps on our agenda.
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    Erweiterbarkeit multimedialer Dokumentensysteme zur dynamischen Anpassung an anwendungsspezifische Anforderungen
    (2004) Hauser, Jürgen; Rothermel, Kurt (Prof. Dr.)
    Multimedia-Präsentationen stellen hohe technische und programmiersprachliche Anforderungen an ihren Ersteller. Grundlage multimedialer Präsentationen sind so genannte Multimedia-Dokumente. Durch die Verwendung von Multimedia-Dokumenten kann der Erstellungsprozess definiert und strukturiert werden. Multimedia-Präsentationen sind durch ihre Zeitabhängigkeit und die Interaktionsmöglichkeiten, die den Verlauf der Präsentation beeinflussen, gekennzeichnet. Damit unterscheiden sie sich grundlegend von textuellen oder statischen Dokumenten. Die Weitergabe von statischen Dokumenten erfolgt nach einer Ausgabe über den Drucker im Allgemeinen in Papierform. Multimedia-Dokumente werden dem Benutzer immer auf einem Rechner präsentiert. Die Zeitabhängigkeit von Multimedia-Präsentationen wurde bereits in vielen wissenschaftlichen Publikationen behandelt. Die vorliegende Abhandlung widmet sich daher hauptsächlich den Interaktionsmöglichkeiten. Beim näheren Betrachten der Interaktion ist zu erkennen, dass sie vom jeweiligen Anwendungsgebiet, in dem das Multimedia-Dokument eingesetzt werden soll, abhängt. Neben der Interaktion selbst ist die Reaktion der Präsentation auf Interaktionen von Bedeutung. Letztendlich unterscheiden sich die Anwendungsgebiete in der Interaktionsform und den Reaktionen der Präsentation. Diese Unterschiede sollten in der Spezifikationssprache für Multimedia-Dokumente sichtbar sein. In der Literatur gibt es zwei unterschiedliche Ansätze für Spezifikationssprachen. Der erste Ansatz sind generische Sprachen. Sie führen zu einem hohen Aufwand bei der Erstellung, da sie anwendungsunabhängig sind und damit den Autor nicht unterstützen. Anwendungsspezifische Spezifikationssprachen legen sich auf ein Anwendungsgebiet fest. Neue Anwendungsgebiete erfordern eine Neuentwicklung und bedeuten eine neue Benutzungsschnittstelle für den Autor. Viele unterschiedliche Systeme und Speicherformate erhöhen den Verwaltungsaufwand und erschweren die Weiterverarbeitung der Dokumente, beispielsweise in bibliographischen Nachweissystemen. In dieser Abhandlung wird ein erweiterbarer Ansatz vorgestellt. Für den erweiterbaren Ansatz wird ein Meta-Dokumentenmodell entwickelt, das die Eigenschaften der Spezifikationssprachen zusammenfasst, die unabhängig vom Anwendungsgebiet sind. Für konkrete Anwendungsgebiete werden Spezifikationssprachen als Instanz dieses Meta-Dokumentenmodells zur Verfügung gestellt. Die Erweiterbarkeit des Ansatzes bedeutet, dass sowohl in einem Autorenwerkzeug als auch im zugehörigen Präsentationssystem die Unterstützung für ein neues Anwendungsgebiet nachträglich hinzugefügt werden kann. Die Implementierung einer Spezifikationssprache, als Erweiterung des Präsentationssystems, soll mit einem möglichst geringem Aufwand verbunden sein. Dazu wird eine modulare Architektur für ein erweiterbares Präsentationssystem vorgeschlagen. Für die Präsentation eines Dokuments müssen alle benötigten Erweiterungen dynamisch zur Laufzeit in die Architektur eingefügt werden. Idealerweise erfolgt dies ohne Zutun des Autors oder Benutzers automatisch durch das Präsentationssystem. Damit beschreibt das Transferformat für Dokumente, das ebenfalls die Erweiterbarkeit unterstützen muss, nicht nur die Struktur der Dokumente, sondern auch die Konfiguration des Präsentationssystems zur Präsentationszeit. Neben der Entwicklung des Meta-Dokumentenmodells und des erweiterbaren Präsentationssystems wird ein ebenfalls dynamisch erweiterbares Autorenwerkzeug konzipiert. Die Erweiterbarkeit des Ansatzes soll im Autorenwerkzeug minimale Auswirkungen auf die Benutzungsschnittstelle haben. Aus diesem Grund greift die Benutzungsschnittstelle zur Erstellung von Multimedia-Dokumenten nur auf Eigenschaften des Meta-Dokumentenmodells zurück. Neben der Erweiterbarkeit werden Konzepte zur Vereinfachung des Spezifikationsprozesses untersucht.
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    The AnT project : on the simulation and analysis of dynamical systems
    (2004) Schanz, Michael; Levi, Paul (Prof. Dr. rer. nat. habil.)
    In this work, a the software project AnT is presented. This project is about a simulation and analysis tool for dynamical systems, whereby it was aimed right from the start, that not only a broad spectrum of dynamical systems is supported, but many investigation methods as well. This thesis is structured as follows: In chapter one (Introduction) a motivation and an overview about the main topics and the involved scientific disciplines is given and among others, the notions of simulation and analysis and their prerequisites are defined and described. The modeling and especially the mathematical modeling are considered in more detail as well as the tasks of interactive and non-interactive simulation. Chapter two (The AnT project) provides an overview about the software - its aims, requirements and features. Some historical and technical remarks are given together with some basic principles and facts about the functionality and a short guidance how to use this software and its features. In the third chapter (Supported classes of dynamical systems), the notion of a dynamical system is defined and described in this context and the most important classes of dynamical systems supported by the AnT software package including their main characteristic properties are listed. For each addresses class of dynamical systems at least one typical and illustrative representative is presented. In chapter four (Scanning dynamical systems), the notion of scanning is described and its importance in the field of nonlinear dynamics is emphasized. The different types of scan possibilities and procedures provided by the software are explained as well as the meaning of a scan item and a scan item sequence. Directly connected with the scanning of a dynamical system is the investigation or analysis of the dynamic behavior, because in most of the cases one is not only interested in the investigation under some fixed conditions but under varying conditions. For the analysis of dynamical systems, several methods are developed in the meanwhile. The methods, which are already implemented in the AnT software and hence available, are presented in chapter five (Supported investigation methods). The investigation of dynamical systems is the most important task in the field of nonlinear dynamics, because it represents the basis for prediction and forecasting of the dynamics as well as improvement and enhancement of the used or derived mathematical models. Therefore, a lot of examples are given in this chapter where the supported investigation methods are applied and illustrated. In chapter six (Simulating and investigating dynamical systems), a more detailed description of the software architecture and applied concepts is given. Especially the most important concepts of transitions and machines designed for the simulation and the investigation are explained and illustrated. The necessity of distributed computing is addressed to in chapter seven (Distributed computing), where the capability of the software to run in distributed mode to solve time consuming investigation tasks in parallel on several workstations or nodes of a cluster is described. The used client/server architecture is presented together with the developed network protocol. Many diagrams and figures in this work are based on the result of time consuming computations and could not have been prepared without the important distributed computing feature of the AnT software package. In chapters eight (AnT-gui: the graphical user interface) and nine (Visualization of dynamical systems), the graphical user interface, which guides a user through the initialization phase and the visualization capabilities of the software were presented, before in chapter ten (Numerical aspects of simulation) some remarks about numerics and scientific computing are elucidated. In chapter eleven (Examples), further illustrative examples of the functionality of the software are given including several scans not only with respect to system parameters but also with respect to initial values and even method parameters. The work closes with chapter twelve (Conclusion), where the main advantages of the AnT software package and the future extensions are presented, together with a short overview about related software projects.