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1. Grundlagen der Softwarevisualisierung Johannes Bohnet und Jürgen Döllner 2. Visualisierung und Exploration von Softwaresystemen mit dem Werkzeug SHriMP/Creole Alexander Gierak 3. Annex: SHriMP/Creole in der Anwendung Nebojsa Lazic 4. Metrikbasierte Softwarevisualisierung mit dem Reverse-Engineering-Werkzeug CodeCrawler Daniel Brinkmann 5. Annex: CodeCrawler in der Anwendung Benjamin Hagedorn 6. Quellcodezeilenbasierte Softwarevisualisierung Nebojsa Lazic 7. Landschafts- und Stadtmetaphern zur Softwarevisualisierung Benjamin Hagedorn 8. Visualisierung von Softwareevolution Michael Schöbel 9. Ergebnisse und Ausblick Johannes Bohnet Literaturverzeichnis Autorenverzeichnis
1 Einleitung 1.1 Motivation 1.2 Aufgabenstellung 1.3 Aufbau der Arbeit 2 Fachliches Umfeld 2.1 Grid Computing 2.2 Idle Time Computing 3 Ressourcenpartitionierung 3.1 Ressourcenpartitionierung und Scheduling 3.2 Ressourcenpartitionierung in Idle Time Computing 3.2.1 Administrative Kontrolle der Ressourcen 3.2.2 Mindestgarantien zur Sicherstellung der Lauffähigkeit 3.3 Vorhandene Lösungen und verwandte Arbeiten 3.3.3 Ressourcenmanagement im Globus Toolkit 3.3.4 Ressourcenmanagement in Condor 3.3.5 Das GARA Framework 3.3.6 Distributed Resource Management Application API 3.3.7 Grid Resource Allocation Agreement Protocol 3.3.8 SNAP 3.3.9 OGSI-Agreement 3.3.10 PBS/Maui und andere Batch Systeme 3.3.11 Wide Area Distributed Computing 3.3.12 Weitere verwandte Arbeiten 3.3.13 Überlegungen zum Ressourcenbedarf 4 Ressourcenkontrolle in Desktopbetriebssystemen 4.1 Ressourcen 4.2 Ressourcenpartitionierung unter Linux 4.2.14 Festplattenkapazität 4.2.15 Arbeitsspeicher 4.2.16 Netzwerkbandbreite 4.2.17 CPU Kapazität 4.3 Ressourcenpartitionierung unter Microsoft Windows XP 4.3.18 Festplattenkapazität 4.3.19 Arbeitsspeicher 4.3.20 Netzwerkbandbreite 4.3.21 CPU Kapazität 4.4 Fazit 5 Entwurf und Design des Frameworks 5.1 Entwurfsgrundlage - Komponentenarchitektur 5.2 Architektur 5.2.22 Broker Server 5.2.23 Broker Software auf den Clients 5.2.24 Schnittstellen 5.3 Komponententypmodell 5.4 Ressourcenidentifikation und Ressourcenzuordnung 5.5 Anbindung ans Grid 5.6 Datenbankentwurf 5.7 XML RPC Schnittstelle 6 Implementierung 6.1 Broker Server 6.1.25 Datenbank 6.1.26 Komponenten 6.1.27 Webserverskripte 6.1.28 Database Crawler 6.2 Komponenten 6.2.29 Network 6.2.30 DSCP 6.2.31 Quota 6.2.32 FSF 6.3 Linux Client 6.3.33 Broker Client 6.3.34 Komponenten 6.4 Windows Client 6.5 Abhängigkeiten 7 Evaluierung 7.1 Durchgeführte Test- und Anwendungsfälle 7.1.35 Test der Clientsoftware 7.1.36 Test der Serversoftware 7.1.37 Durchführbare Anwendungsfälle 7.2 Evaluierung der Frameworkimplementierung 7.2.38 Performanz der Serverimplementierung 7.2.39 Zuverlässigkeit der Partitionierungen 7.3 Evaluierung von Traffic Shaping mit iproute2 7.3.40 Szenario 1 7.3.41 Szenario 2 7.3.42 Szenario 3 7.3.43 Fazit 8 Zusammenfassung und Ausblick 8.1 Fazit 8.2 Weiterentwicklung 8.2.44 Weiterentwicklungen auf Entwurfsebene 8.2.45 Weiterentwicklungen auf Implementierungsebene Anhang A: Details zum Datenbankentwurf Anhang B: Bildschirmfotos der Weboberfläche Anhang C: Quellcode Linux Broker Client Anhang D: Inhalt des beiliegenden Datenträgers
Vorwort 1. Einleitung 2. Statische vs. dynamische Analyse 3. Kriterien für den Erfolg statischer Quellcodeanalysemethoden 3.1. Theoretische Vorüberlegungen 3.2. 1. Kriterium: Verfügbarkeit des Quellcodes 3.3. 2. Kriterium: Unterstützung der Programmiersprache 3.4. 3. Kriterium: Zulassung von „echten“ Programmen der Problemdomäne 3.5. 4. Kriterium: Bewältigung der auftretenden Komplexität 3.6. 5. Kriterium: Schutz vor böswilliger Speichermanipulation 3.7. 6. Kriterium: Garantie für die Umgebung des laufenden Prozesses 3.8. Fazit 3.9. Verwandte Arbeiten 4. Bewertung von statischen Methoden für C/C++ typische Programme 4.1. Hintergrund 4.2. Prämissen 4.3. 1. Problemfeld: Programmgröße und Interferenz 4.4. 2. Problemfeld: Semantik 4.5. 3. Problemfeld: Programmfluss 4.6. 4. Problemfeld: Zeigerarithmetik 4.7. Dynamische Konzepte zur Erfüllung des fünften Kriteriums auf Quellcodebasis 4.8. Fazit 4.9. Verwandte Arbeiten 5. Kriterien für den Erfolg dynamischer Ansätze 5.1. Hintergrund 5.2. Verfügbarkeit des Quellcodes 5.3. Unterstützung der Programmiersprache 5.4. Zulassung von „echten“ Programmen aus der Problemdomäne 5.5. Bewältigung der auftretenden Komplexität 5.6. Schutz vor böswilliger Speichermanipulation 5.7. Garantie für die Umgebung des laufenden Prozesses 5.8. Fazit 6. Klassifikation und Evaluation dynamischer Ansätze 6.1. Hintergrund 6.2. Quellcodesubstitution 6.3. Binärcodemodifikation/Binary-Rewriting 6.4. Maschinencodeinterpreter 6.5. Intrusion-Detection-Systeme 6.6. Virtuelle Maschinen/Safe Languages 6.7. Mechanismen zur „Härtung“ von bestehenden Code 6.8. SandBoxing/System-Call-Interposition 6.9. Herkömmliche Betriebssystemmittel 6.10. Access-Control-Lists/Domain-Type-Enforcement 6.11. Fazit 7. Sichere Ausführung nicht vertrauenswürdiger Programme im Kontext von RealTimeBattle 7.1. Vorstellung von RealTimeBattle 7.2. Charakterisierung des Problems 7.3. Alternative Lösungsvarianten/Rekapitulation 7.4. Übertragung der Ergebnisse statischer Analysemethoden auf RealTimeBattle 7.5. Übertragung der Ergebnisse dynamischer Analysemethoden auf RealTimeBattle 7.5.1. Vorstellung der RSBAC basierten Lösung 7.5.2. Vorstellung der Systrace basierten Lösung 7.6. Fazit 7.7. Verwandte Arbeiten 8. Sichere Ausführung nicht vertrauenswürdiger Programme im Kontext von Asparagus 8.1. Vorstellung von Asparagus 8.2. Charakterisierung des Problems 8.3. Lösung des Problems 8.4. Fazit 8.5. Verwandte Arbeiten 9. Sichere Ausführung nicht vertrauenswürdiger Programme im Kontext vom DCL 9.1. Vorstellung des DCL 9.2. Charakterisierung des Problems 9.3. Experimente im DCL und die jeweilige Lösung 9.3.1. Foucaultsches Pendel 9.3.2. Lego Mindstorm Roboter 9.3.3. Hau den Lukas 9.4. Fazit 9.5. Verwandte Arbeiten 10. Sichere Ausführung nicht vertrauenswürdiger Programme im Kontext der semiautomatischen Korrektur von Betriebssystemarchitektur-Übungsaufgaben 10.1. Vorstellung des Übungsbetriebes zur Vorlesung „Betriebssystsemarchitektur 10.2. Charakterisierung des Problems 10.3. Lösungsvorschläge 10.3.1. Lösungsvorschläge für das Authentifizierungs-Problem 10.3.2. Lösungsvorschläge für das Transport-Problem 10.3.3. Lösungsvorschläge für das Build-Problem 10.3.4. Lösungsvorschläge für das Ausführungs-Problem 10.3.5. Lösungsvorschläge für das Ressourcen-Problem 10.3.6. Lösungsvorschläge für das Portabilitäts-Problem 10.4. Fazit 10.5. Verwandte Arbeiten 11. Schlussbetrachtungen Literaturverzeichnis Anhang -create_guardedrobot.sh: Die RealTimeBattle Security Infrastructure -vuln.c: Ein durch Pufferüberlauf ausnutzbares Programm -exploit.c: Ein Beispielexploit für vuln.c. -aufg43.c: Lösung für eine Aufgabe im Rahmen der Betriebssystemarchitektur-Übung -Handout: Sichere Ausführung nicht vertrauenswürdiger Programme
1. Applikationen für weitverteiltes Rechnen Dennis Klemann, Lars Schmidt-Bielicke, Philipp Seuring 2. Das Globus-Toolkit Dietmar Bremser, Alexis Krepp, Tobias Rausch 3. Open Grid Services Architecture Lars Trieloff 4. Condor, Condor-G, Classad Stefan Henze, Kai Köhne 5. The Cactus Framework Thomas Hille, Martin Karlsch 6. High Performance Scheduler mit Maui/PBS Ole Weidner, Jörg Schummer, Benedikt Meuthrath 7. Bandbreiten-Monitoring mit NWS Alexander Ritter, Gregor Höfert 8. The Paradyn Parallel Performance Measurement Tool Jens Ulferts, Christian Liesegang 9. Grid-Applikationen in der Praxis Steffen Bach, Michael Blume, Helge Issel
Quantified Boolean formulas (QBFs) play an important role in theoretical computer science. QBF extends propositional logic in such a way that many advanced forms of reasoning can be easily formulated and evaluated. In this dissertation we present our ZQSAT, which is an algorithm for evaluating quantified Boolean formulas. ZQSAT is based on ZBDD: Zero-Suppressed Binary Decision Diagram , which is a variant of BDD, and an adopted version of the DPLL algorithm. It has been implemented in C using the CUDD: Colorado University Decision Diagram package. The capability of ZBDDs in storing sets of subsets efficiently enabled us to store the clauses of a QBF very compactly and let us to embed the notion of memoization to the DPLL algorithm. These points led us to implement the search algorithm in such a way that we could store and reuse the results of all previously solved subformulas with a little overheads. ZQSAT can solve some sets of standard QBF benchmark problems (known to be hard for DPLL based algorithms) faster than the best existing solvers. In addition to prenex-CNF, ZQSAT accepts prenex-NNF formulas. We show and prove how this capability can be exponentially beneficial.
1 Introduction 1.1 Project formulation 1.2 Our contribution 2 Pedagogical Aspect 4 2.1 Modern teaching 2.2 Our Contribution 2.2.1 Autonomous and exploratory learning 2.2.2 Human machine interaction 2.2.3 Short multimedia clips 3 Ontology Aspect 3.1 Ontology driven expert systems 3.2 Our contribution 3.2.1 Ontology language 3.2.2 Concept Taxonomy 3.2.3 Knowledge base annotation 3.2.4 Description Logics 4 Natural language approach 4.1 Natural language processing in computer science 4.2 Our contribution 4.2.1 Explored strategies 4.2.2 Word equivalence 4.2.3 Semantic interpretation 4.2.4 Various problems 5 Information Retrieval Aspect 5.1 Modern information retrieval 5.2 Our contribution 5.2.1 Semantic query generation 5.2.2 Semantic relatedness 6 Implementation 6.1 Prototypes 6.2 Semantic layer architecture 6.3 Development 7 Experiments 7.1 Description of the experiments 7.2 General characteristics of the three sessions, instructions and procedure 7.3 First Session 7.4 Second Session 7.5 Third Session 7.6 Discussion and conclusion 8 Conclusion and future work 8.1 Conclusion 8.2 Open questions A Description Logics B Probabilistic context-free grammars
The goal of a Brain-Computer Interface (BCI) consists of the development of a unidirectional interface between a human and a computer to allow control of a device only via brain signals. While the BCI systems of almost all other groups require the user to be trained over several weeks or even months, the group of Prof. Dr. Klaus-Robert Müller in Berlin and Potsdam, which I belong to, was one of the first research groups in this field which used machine learning techniques on a large scale. The adaptivity of the processing system to the individual brain patterns of the subject confers huge advantages for the user. Thus BCI research is considered a hot topic in machine learning and computer science. It requires interdisciplinary cooperation between disparate fields such as neuroscience, since only by combining machine learning and signal processing techniques based on neurophysiological knowledge will the largest progress be made. In this work I particularly deal with my part of this project, which lies mainly in the area of computer science. I have considered the following three main points: <b>Establishing a performance measure based on information theory:</b> I have critically illuminated the assumptions of Shannon's information transfer rate for application in a BCI context. By establishing suitable coding strategies I was able to show that this theoretical measure approximates quite well to what is practically achieveable. <b>Transfer and development of suitable signal processing and machine learning techniques:</b> One substantial component of my work was to develop several machine learning and signal processing algorithms to improve the efficiency of a BCI. Based on the neurophysiological knowledge that several independent EEG features can be observed for some mental states, I have developed a method for combining different and maybe independent features which improved performance. In some cases the performance of the combination algorithm outperforms the best single performance by more than 50 %. Furthermore, I have theoretically and practically addressed via the development of suitable algorithms the question of the optimal number of classes which should be used for a BCI. It transpired that with BCI performances reported so far, three or four different mental states are optimal. For another extension I have combined ideas from signal processing with those of machine learning since a high gain can be achieved if the temporal filtering, i.e., the choice of frequency bands, is automatically adapted to each subject individually. <b>Implementation of the Berlin brain computer interface and realization of suitable experiments:</b> Finally a further substantial component of my work was to realize an online BCI system which includes the developed methods, but is also flexible enough to allow the simple realization of new algorithms and ideas. So far, bitrates of up to 40 bits per minute have been achieved with this system by absolutely untrained users which, compared to results of other groups, is highly successful.
Advances in biotechnologies rapidly increase the number of molecules of a cell which can be observed simultaneously. This includes expression levels of thousands or ten-thousands of genes as well as concentration levels of metabolites or proteins. Such Profile data, observed at different times or at different experimental conditions (e.g., heat or dry stress), show how the biological experiment is reflected on the molecular level. This information is helpful to understand the molecular behaviour and to identify molecules or combination of molecules that characterise specific biological condition (e.g., disease). This work shows the potentials of component extraction algorithms to identify the major factors which influenced the observed data. This can be the expected experimental factors such as the time or temperature as well as unexpected factors such as technical artefacts or even unknown biological behaviour. Extracting components means to reduce the very high-dimensional data to a small set of new variables termed components. Each component is a combination of all original variables. The classical approach for that purpose is the principal component analysis (PCA). It is shown that, in contrast to PCA which maximises the variance only, modern approaches such as independent component analysis (ICA) are more suitable for analysing molecular data. The condition of independence between components of ICA fits more naturally our assumption of individual (independent) factors which influence the data. This higher potential of ICA is demonstrated by a crossing experiment of the model plant Arabidopsis thaliana (Thale Cress). The experimental factors could be well identified and, in addition, ICA could even detect a technical artefact. However, in continuously observations such as in time experiments, the data show, in general, a nonlinear distribution. To analyse such nonlinear data, a nonlinear extension of PCA is used. This nonlinear PCA (NLPCA) is based on a neural network algorithm. The algorithm is adapted to be applicable to incomplete molecular data sets. Thus, it provides also the ability to estimate the missing data. The potential of nonlinear PCA to identify nonlinear factors is demonstrated by a cold stress experiment of Arabidopsis thaliana. The results of component analysis can be used to build a molecular network model. Since it includes functional dependencies it is termed functional network. Applied to the cold stress data, it is shown that functional networks are appropriate to visualise biological processes and thereby reveals molecular dynamics.
Inhaltsverzeichnis 1 Einführung 2 Aspektorientierte Programmierung 2.1 Ein System als Menge von Eigenschaften 2.2 Aspekte 2.3 Aspektweber 2.4 Vorteile Aspektorientierter Programmierung 2.5 Kategorisierung der Techniken und Werkzeuge f ¨ ur Aspektorientierte Programmierung 3 Techniken und Werkzeuge zur Analyse Aspektorientierter Softwareprogramme 3.1 Virtual Source File 3.2 FEAT 3.3 JQuery 3.4 Aspect Mining Tool 4 Techniken und Werkzeuge zum Entwurf Aspektorientierter Softwareprogramme 4.1 Concern Space Modeling Schema 4.2 Modellierung von Aspekten mit UML 4.3 CoCompose 4.4 Codagen Architect 5 Techniken und Werkzeuge zur Implementierung Aspektorientierter Softwareprogramme 5.1 Statische Aspektweber 5.2 Dynamische Aspektweber 6 Zusammenfassung
Three quantum cryptographic protocols of multiuser quantum networks with embedded authentication, allowing quantum key distribution or quantum direct communication, are discussed in this work. The security of the protocols against different types of attacks is analysed with a focus on various impersonation attacks and the man-in-the-middle attack. On the basis of the security analyses several improvements are suggested and implemented in order to adjust the investigated vulnerabilities. Furthermore, the impact of the eavesdropping test procedure on impersonation attacks is outlined. The framework of a general eavesdropping test is proposed to provide additional protection against security risks in impersonation attacks.
Aufzählen von DNA-Codes
(2006)
In dieser Arbeit wird ein Modell zum Aufzählen von DNA-Codes entwickelt. Indem eine Ordnung auf der Menge aller DNA-Codewörter eingeführt und auf die Menge aller Codes erweitert wird, erlaubt das Modell das Auffinden von DNA-Codes mit bestimmten Eigenschaften, wie Überlappungsfreiheit, Konformität, Kommafreiheit, Stickyfreiheit, Überhangfreiheit, Teilwortkonformität und anderer bezüglich einer gegebenen Involution auf der Menge der Codewörter. Ein auf Grundlage des geschaffenen Modells entstandenes Werkzeug erlaubt das Suchen von Codes mit beliebigen Kombinationen von Codeeigenschaften. Ein weiterer wesentlicher Bestandteil dieser Arbeit ist die Untersuchung der Optimalität von DNA-Codes bezüglich ihrer Informationsrate sowie das Finden solider DNA-Codes.
An increasing number of applications requires user interfaces that facilitate the handling of large geodata sets. Using virtual 3D city models, complex geospatial information can be communicated visually in an intuitive way. Therefore, real-time visualization of virtual 3D city models represents a key functionality for interactive exploration, presentation, analysis, and manipulation of geospatial data. This thesis concentrates on the development and implementation of concepts and techniques for real-time city model visualization. It discusses rendering algorithms as well as complementary modeling concepts and interaction techniques. Particularly, the work introduces a new real-time rendering technique to handle city models of high complexity concerning texture size and number of textures. Such models are difficult to handle by current technology, primarily due to two problems: - Limited texture memory: The amount of simultaneously usable texture data is limited by the memory of the graphics hardware. - Limited number of textures: Using several thousand different textures simultaneously causes significant performance problems due to texture switch operations during rendering. The multiresolution texture atlases approach, introduced in this thesis, overcomes both problems. During rendering, it permanently maintains a small set of textures that are sufficient for the current view and the screen resolution available. The efficiency of multiresolution texture atlases is evaluated in performance tests. To summarize, the results demonstrate that the following goals have been achieved: - Real-time rendering becomes possible for 3D scenes whose amount of texture data exceeds the main memory capacity. - Overhead due to texture switches is kept permanently low, so that the number of different textures has no significant effect on the rendering frame rate. Furthermore, this thesis introduces two new approaches for real-time city model visualization that use textures as core visualization elements: - An approach for visualization of thematic information. - An approach for illustrative visualization of 3D city models. Both techniques demonstrate that multiresolution texture atlases provide a basic functionality for the development of new applications and systems in the domain of city model visualization.
Since 2002, keywords like service-oriented engineering, service-oriented computing, and service-oriented architecture have been widely used in research, education, and enterprises. These and related terms are often misunderstood or used incorrectly. To correct these misunderstandings, a deeper knowledge of the concepts, the historical backgrounds, and an overview of service-oriented architectures is demanded and given in this paper.
Dynamics in urban environments encompasses complex processes and phenomena such as related to movement (e.g.,traffic, people) and development (e.g., construction, settlement). This paper presents novel methods for creating human-centric illustrative maps for visualizing the movement dynamics in virtual 3D environments. The methods allow a viewer to gain rapid insight into traffic density and flow. The illustrative maps represent vehicle behavior as light threads. Light threads are a familiar visual metaphor caused by moving light sources producing streaks in a long-exposure photograph. A vehicle’s front and rear lights produce light threads that convey its direction of motion as well as its velocity and acceleration. The accumulation of light threads allows a viewer to quickly perceive traffic flow and density. The light-thread technique is a key element to effective visualization systems for analytic reasoning, exploration, and monitoring of geospatial processes.
This thesis discusses challenges in IT security education, points out a gap between e-learning and practical education, and presents a work to fill the gap. E-learning is a flexible and personalized alternative to traditional education. Nonetheless, existing e-learning systems for IT security education have difficulties in delivering hands-on experience because of the lack of proximity. Laboratory environments and practical exercises are indispensable instruction tools to IT security education, but security education in conventional computer laboratories poses particular problems such as immobility as well as high creation and maintenance costs. Hence, there is a need to effectively transform security laboratories and practical exercises into e-learning forms. In this thesis, we introduce the Tele-Lab IT-Security architecture that allows students not only to learn IT security principles, but also to gain hands-on security experience by exercises in an online laboratory environment. In this architecture, virtual machines are used to provide safe user work environments instead of real computers. Thus, traditional laboratory environments can be cloned onto the Internet by software, which increases accessibility to laboratory resources and greatly reduces investment and maintenance costs. Under the Tele-Lab IT-Security framework, a set of technical solutions is also proposed to provide effective functionalities, reliability, security, and performance. The virtual machines with appropriate resource allocation, software installation, and system configurations are used to build lightweight security laboratories on a hosting computer. Reliability and availability of laboratory platforms are covered by a virtual machine management framework. This management framework provides necessary monitoring and administration services to detect and recover critical failures of virtual machines at run time. Considering the risk that virtual machines can be misused for compromising production networks, we present a security management solution to prevent the misuse of laboratory resources by security isolation at the system and network levels. This work is an attempt to bridge the gap between e-learning/tele-teaching and practical IT security education. It is not to substitute conventional teaching in laboratories but to add practical features to e-learning. This thesis demonstrates the possibility to implement hands-on security laboratories on the Internet reliably, securely, and economically.
E-learning is a flexible and personalized alternative to traditional education. Nonetheless, existing e-learning systems for IT security education have difficulties in delivering hands-on experience because of the lack of proximity. Laboratory environments and practical exercises are indispensable instruction tools to IT security education, but security education in con-ventional computer laboratories poses the problem of immobility as well as high creation and maintenance costs. Hence, there is a need to effectively transform security laboratories and practical exercises into e-learning forms. This report introduces the Tele-Lab IT-Security architecture that allows students not only to learn IT security principles, but also to gain hands-on security experience by exercises in an online laboratory environment. In this architecture, virtual machines are used to provide safe user work environments instead of real computers. Thus, traditional laboratory environments can be cloned onto the Internet by software, which increases accessibilities to laboratory resources and greatly reduces investment and maintenance costs. Under the Tele-Lab IT-Security framework, a set of technical solutions is also proposed to provide effective functionalities, reliability, security, and performance. The virtual machines with appropriate resource allocation, software installation, and system configurations are used to build lightweight security laboratories on a hosting computer. Reliability and availability of laboratory platforms are covered by the virtual machine management framework. This management framework provides necessary monitoring and administration services to detect and recover critical failures of virtual machines at run time. Considering the risk that virtual machines can be misused for compromising production networks, we present security management solutions to prevent misuse of laboratory resources by security isolation at the system and network levels. This work is an attempt to bridge the gap between e-learning/tele-teaching and practical IT security education. It is not to substitute conventional teaching in laboratories but to add practical features to e-learning. This report demonstrates the possibility to implement hands-on security laboratories on the Internet reliably, securely, and economically.
With increasing number of applications in Internet and mobile environments, distributed software systems are demanded to be more powerful and flexible, especially in terms of dynamism and security. This dissertation describes my work concerning three aspects: dynamic reconfiguration of component software, security control on middleware applications, and web services dynamic composition. Firstly, I proposed a technology named Routing Based Workflow (RBW) to model the execution and management of collaborative components and realize temporary binding for component instances. The temporary binding means component instances are temporarily loaded into a created execution environment to execute their functions, and then are released to their repository after executions. The temporary binding allows to create an idle execution environment for all collaborative components, on which the change operations can be immediately carried out. The changes on execution environment will result in a new collaboration of all involved components, and also greatly simplifies the classical issues arising from dynamic changes, such as consistency preserving etc. To demonstrate the feasibility of RBW, I created a dynamic secure middleware system - the Smart Data Server Version 3.0 (SDS3). In SDS3, an open source implementation of CORBA is adopted and modified as the communication infrastructure, and three secure components managed by RBW, are created to enhance the security on the access of deployed applications. SDS3 offers multi-level security control on its applications from strategy control to application-specific detail control. For the management by RBW, the strategy control of SDS3 applications could be dynamically changed by reorganizing the collaboration of the three secure components. In addition, I created the Dynamic Services Composer (DSC) based on Apache open source projects, Apache Axis and WSIF. In DSC, RBW is employed to model the interaction and collaboration of web services and to enable the dynamic changes on the flow structure of web services. Finally, overall performance tests were made to evaluate the efficiency of the developed RBW and SDS3. The results demonstrated that temporary binding of component instances makes slight impacts on the execution efficiency of components, and the blackout time arising from dynamic changes can be extremely reduced in any applications.
This paper describes the proof calculus LD for clausal propositional logic, which is a linearized form of the well-known DPLL calculus extended by clause learning. It is motivated by the demand to model how current SAT solvers built on clause learning are working, while abstracting from decision heuristics and implementation details. The calculus is proved sound and terminating. Further, it is shown that both the original DPLL calculus and the conflict-directed backtracking calculus with clause learning, as it is implemented in many current SAT solvers, are complete and proof-confluent instances of the LD calculus.
"Wir gehen multimedial. Kommt ihr mit?" war Aufruf und Leitmotiv der MultimeDies 2007. Es kamen sehr viele mit, vor allem Lehrende und Lernende der Universität Potsdam, aber auch Firmen. Diese Veranstaltung setzt eine Tradition fort, die im Bemühen steht über zukunftsweisende Technologien und Projekte, über Angebote und praktikable Lösungen an der Universität zu informieren. Die Vorträge wurden in kurzen Beiträgen zusammengestellt. Sie gliedern sich in zwei Gruppen, zum einen der Bereitstellung, zum anderen der Nutzung von Multimedia.