Universität Stuttgart
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Item Open Access Partnerübergreifende Geschäftsprozesse und ihre Realisierung in BPEL(2016) Kopp, Oliver; Leymann, Frank (Prof. Dr. Dr. h. c.)Diese Arbeit beschäftigt sich mit Geschäftsprozessen, die die Grenzen von Organisationen überspannen. Solche Geschäftsprozesse werden Choreographien genannt. In der Arbeit wird die CREAM-Methode vorgestellt, die zeigt, wie Choreographien modelliert werden können. Im Gegensatz zu Choreographien bezeichnen Orchestrierungen ausführbare Geschäftsprozesse einer einzelnen Organisation, die Dienste nutzen, um ein Geschäftsziel zu erreichen. Eine Variante der CREAM-Methode erlaubt, von einer Orchestrierung durch Aufteilung der Orchestrierung eine Choreographie zu erhalten. Um hierbei die impliziten orchestrierungsinternen Datenabhängigkeiten in Nachrichtenaustausche zu transformieren, wird der explizite Datenfluss der Orchestrierung benötigt. Die Web Services Business Process Execution Language (BPEL) ist eine verbreitete Sprache zur Modellierung von Geschäftsprozessen. In ihr wird der Datenfluss implizit modelliert und somit wird ein Verfahren benötigt, das den expliziten Datenfluss bestimmt. In dieser Arbeit wird ein solches Verfahren vorgestellt. Um eine Choreographie zu modellieren, wird eine Choreographiesprache benötigt. Zur Identifikation einer geeigneten Sprache werden in dieser Arbeit Kriterien zur Evaluation von Choreographiesprachen vorgestellt und damit Choreographiesprachen im Web-Service-Umfeld bewertet. Da keine der betrachteten Sprachen alle Kriterien erfüllt, wird die Sprache BPEL4Chor vorgestellt, die alle Kriterien erfüllt. Um die wohldefinierte Ausführungssemantik von BPEL wiederzuverwenden, verwendet BPEL4Chor die Sprache BPEL als Beschreibungssprache des Verhaltens jedes Teilnehmers in der Choreographie. BPEL4Chor verwendet analog zu BPEL XML als Serialisierungsformat und spezifiziert keine eigene graphische Repräsentation. Die Business Process Modeling Notation (BPMN) ist der de-facto Standard, um Geschäftsprozesse graphisch darzustellen. Deshalb wird in dieser Arbeit BPMN so erweitert, dass alle in BPEL4Chor verfügbaren Konstrukte mittels BPMN modelliert werden können.Item Open Access Visual Analytics im Kontext der Daten- und Analysequalität am Beispiel von Data Mashups(2016) Behringer, MichaelViele Prozesse und Geschäftsmodelle der Gegenwart basieren auf der Auswertung von Daten. Durch Fortschritte in der Speichertechnologie und Vernetzung ist die Akquisition von Daten heute sehr einfach und wird umfassend genutzt. Das weltweit vorhandene Datenvolumen steigt exponentiell und sorgt für eine zunehmende Komplexität der Analyse. In den letzten Jahren fällt in diesem Zusammenhang öfter der Begriff Visual Analytics. Dieses Forschungsgebiet kombiniert visuelle und automatische Verfahren zur Datenanalyse. Im Rahmen dieser Arbeit werden die Verwendung und die Ziele von Visual Analytics evaluiert und eine neue umfassendere Definition entwickelt. Aus dieser wird eine Erweiterung des Knowledge Discovery-Prozesses abgeleitet und verschiedene Ansätze bewertet. Um die Unterschiede zwischen Data Mining, der Visualisierung und Visual Analytics zu verdeutlichen, werden diese Themengebiete gegenübergestellt und in einem Ordnungsrahmen hinsichtlich verschiedener Dimensionen klassifiziert. Zusätzlich wird untersucht, inwiefern dieser neue Ansatz im Hinblick auf Daten- und Analysequalität eingesetzt werden kann. Abschließend wird auf Basis der gewonnenen Erkenntnisse eine prototypische Implementierung auf Basis von FlexMash, einem an der Universität Stuttgart entwickelten Data Mashup-Werkzeug, beschrieben. Data Mashups vereinfachen die Einbindung von Anwendern ohne technischen Hintergrund und harmonieren daher ausgezeichnet mit Visual Analytics.Item Open Access Process migration in a parallel environment(Stuttgart : Höchstleistungsrechenzentrum, Universität Stuttgart, 2016) Reber, Adrian; Resch, Michael (Prof. Dr.- Ing. Dr. h.c. Dr. h.c. Prof. E.h.)To satisfy the ever increasing demand for computational resources, high performance computing systems are becoming larger and larger. Unfortunately, the tools supporting system management tasks are only slowly adapting to the increase in components in computational clusters. Virtualization provides concepts which make system management tasks easier to implement by providing more flexibility for system administrators. With the help of virtual machine migration, the point in time for certain system management tasks like hardware or software upgrades no longer depends on the usage of the physical hardware. The flexibility to migrate a running virtual machine without significant interruption to the provided service makes it possible to perform system management tasks at the optimal point in time. In most high performance computing systems, however, virtualization is still not implemented. The reason for avoiding virtualization in high performance computing is that there is still an overhead accessing the CPU and I/O devices. This overhead continually decreases and there are different kind of virtualization techniques like para-virtualization and container-based virtualization which minimize this overhead further. With the CPU being one of the primary resources in high performance computing, this work proposes to migrate processes instead of virtual machines thus avoiding any overhead. Process migration can either be seen as an extension to pre-emptive multitasking over system boundaries or as a special form of checkpointing and restarting. In the scope of this work process migration is based on checkpointing and restarting as it is already an established technique in the field of fault tolerance. From the existing checkpointing and restarting implementations, the best suited implementation for process migration purposes was selected. One of the important requirements of the checkpointing and restarting implementation is transparency. Providing transparent process migration is important enable the migration of any process without prerequisites like re-compilation or running in a specially prepared environment. With process migration based on checkpointing and restarting, the next step towards providing process migration in a high performance computing environment is to support the migration of parallel processes. Using MPI is a common method of parallelizing applications and therefore process migration has to be integrated with an MPI implementation. The previously selected checkpointing and restarting implementation was integrated in an MPI implementation, and thus enabling the migration of parallel processes. With the help of different test cases the implemented process migration was analyzed, especially in regards to the time required to migrated a process and the advantages of optimizations to reduce the process’ downtime during migration.Item Open Access Privatheit im Gesundheitsspiel Candy Castle(2016) Giebler, CorinnaDie zunehmende Verwendung elektronischer Endgeräte stellt die heutige Gesellschaft vor das große Problem der Datenprivatheit. Die digitalen Helfer verwalten verschiedenste persönliche Daten, auf die wiederum eine Vielzahl von Anwendungen Zugriff hat. Selten ist es dem Benutzer möglich, direkten Einfluss oder auch nur Einblick in die Verwendung seiner Daten zu erlangen. Besonders in der Kritik stehen hierbei mobile Plattformen, wie Smartphones oder Tablets. Die Applikationen, oder kurz Apps, für diese Plattformen verfügen nur selten über Datenschutzerklärungen oder Maßnahmen zum Datenschutz. Auch ist es auf bestimmten Betriebssystemen nicht möglich, die Berechtigungen einer App einzuschränken. Dabei werden gerade diese mobilen Endgeräte mehr und mehr zur Verwaltung sensibler Daten verwendet. Hierzu gehören inzwischen auch medizinische Daten, die mithilfe diverser Gesundheits-Apps aufgezeichnet und verarbeitet werden können. Da es sich bei diesen medizinischen Werten um sehr private Daten handelt, sind diese besonders schützenswert. Zudem sollte der Nutzer einer solchen Gesundheits-App stets wissen, was mit seinen Daten geschieht und die Kontrolle über ihre Verwendung innehaben. In dieser Arbeit soll darum erörtert werden, wie sich die persönlichen Daten mithilfe eines Berechtigungssystems schützen lassen. Zunächst wird hierfür ein Anforderungskatalog ermittelt, der neben Anforderungen an Funktionalität und Bedienbarkeit auch Forderungen an Privatheit und Nutzerbestimmung stellt. Mithilfe dieses Katalogs wird anschließend ein Gesundheitsspiel für Kinder mit Diabetes weiterentwickelt und um Privatheitsaspekte erweitert. So entsteht ein Prototyp für ein Spiel, dessen Privatheitsgrad vom Benutzer einstellbar ist. Zuletzt wird gezeigt werden, dass die zuvor gestellten Anforderungen erfüllt sind und dass verarbeitete Daten auch vor unerlaubtem Zugriff geschützt werden können.Item Open Access Cost optimization for data placement strategies in an analytical cloud service(2016) Saleem, Muhammad UsmanAnalyzing a large amount of business-relevant data in near-realtime in order to assist decision making became a crucial requirement for many businesses in the last years. Therefore, all major database system vendors offer solutions that assist customers in this requirement with systems that are specially tuned for accelerating analytical workloads. Before the decision is made to buy such a huge and expensive solution, customers are interested in getting a detailed workload analysis in order to estimate potential benefits. Therefore, a more agile solution is desirable having lower barriers to entry that allows customers to assess analytical solutions for their workloads and lets data scientists experiment with available data on test systems before rolling out valuable analytical reports on a production system. In such a scenario where separate systems are deployed for handling transactional workloads of daily customers business and conducting business analytics on either a cloud service or a dedicated accelerator appliance, data management and placement strategies are of high importance. Multiple approaches exist for keeping the data set in-sync and guaranteeing data coherence with unique characteristics regarding important metrics that impact query performance, such as the latency when data will be propagated, achievable throughputs for larger data volumes, or the amount of required CPU to detect and deploy data changes. So the important heuristics are analyzed and evolved in order to develop a general model for data placement and maintenance strategies. Based on this theoretical model, a prototype is also implemented that predicts these metrics.Item Open Access Code execution reports: visually augmented summaries of executed source code fragments(2016) Siddiqui, Hafiz AmmarUnderstanding a fragment of code is important for developers as it enables them to optimize, debug and extend it. Developers adopt different procedures for understanding a piece of code, which involves going through the source code, documentation, and profilers results. Various code comprehension techniques have suggested code summarization approaches, which generates the intended behavior of code in natural language text. In this thesis, we present an approach to summarize the actual behavior of a method during its execution. For this purpose, we create a framework that facilitates the generation of interactive and web-based natural language reports with small embedded word-size visualizations. Then, we develop a tool that profiles a method for runtime behavior, and then it processes the information. The tool uses our framework to generate a visually augmented natural language summary report that explains the behavior of the code. In the end, we conduct a small user study to evaluate the quality of our code execution reports.Item Open Access Rendering of densely recorded light fields(2016) Zahn, SebastianLight fields present an alternate approach for producing images of a high degree of realism, by capturing real world data in the form of images, or by traditional techniques like raytracing a synthetic scene. In both cases, the produced data can be utilized to render images from positions which were previously not recorded or with different camera parameters and configurations. The resolution and spatial density, at which such light fields are recorded, influence the mass of produced data that has to be handled. This work focuses on densely recorded light fields and attempts to produce synthesized images computed from the available data, defined by a camera moving through space. Synthesized cameras are also able to change their aperture size and focus setting. Rendered cameras behave according to the thin lens model. A method for extraction of relevant light field images is proposed. For rendering of the data, two different approaches are evaluated. The first approach collects rays which are present in the light field in synthetic sensor plates. In an alternative approach, rays are collected in a standard hash map, and rendered by constructing and querying a kd-tree. Both approaches yield a set of properties which make them useful in different scenarios, and can also be combined to an hybrid renderer. The proposed system is intended to run on several machines in parallel.Item Open Access Modeling the interface between morphology and syntax in data-driven dependency parsing(2016) Seeker, Wolfgang; Kuhn, Jonas (Prof. Dr.)When people formulate sentences in a language, they follow a set of rules specific to that language that defines how words must be put together in order to express the intended meaning. These rules are called the grammar of the language. Languages have essentially two ways of encoding grammatical information: word order or word form. English uses primarily word order to encode different meanings, but many other languages change the form of the words themselves to express their grammatical function in the sentence. These languages are commonly subsumed under the term morphologically rich languages. Parsing is the automatic process for predicting the grammatical structure of a sentence. Since grammatical structure guides the way we understand sentences, parsing is a key component in computer programs that try to automatically understand what people say and write. This dissertation is about parsing and specifically about parsing languages with a rich morphology, which encode grammatical information in the form of words. Today’s parsing models for automatic parsing were developed for English and achieve good results on this language. However, when applied to other languages, a significant drop in performance is usually observed. The standard model for parsing is a pipeline model that separates the parsing process into different steps, in particular it separates the morphological analysis, i.e. the analysis of word forms, from the actual parsing step. This dissertation argues that this separation is one of the reasons for the performance drop of standard parsers when applied to other languages than English. An analysis is presented that exposes the connection between the morphological system of a language and the errors of a standard parsing model. In a second series of experiments, we show that knowledge about the syntactic structure of sentence can support the prediction of morphological information. We then argue for an alternative approach that models morphological analysis and syntactic analysis jointly instead of separating them. We support this argumentation with empirical evidence by implementing two parsers that model the relationship between morphology and syntax in two different but complementary ways.Item Open Access In-network packet priority adaptation for networked control systems(2016) Zinkler, StephanSharing the network between Networked Control System (NCS) having strict demands with respect to latency and jitter and applications only requiring best-effort service leads to multiple problems. An important task to consider is how to prioritize individual types of traffic in such a way that the necessary guarantees for an NCS to be stable can still be given. While there are ways to prioritize the more important control traffic of an NCS over best-effort traffic sharing the same network, a more sophisticated approach has to be found in order to handle multiple NCS sharing the highest priority. In this thesis, in-network priority scheduling applications with a global view on the network are developed in order to schedule and prioritize individual NCS such that their stability can be guaranteed while sharing the network between multiple NCS. This thesis deals with in-network packet priority scheduling for Networked Control Systems. Using Data Plane Development Kit (DPDK) to achieve a Network Function Virtualization (NFV) based approach, a priority scheduling application is implemented in a middlebox to handle continuous priorities. This application could be instantiated and migrated within the network while simultaneously using Software Defined Networking (SDN) to route the traffic to the respective nodes. Additionally, this approach is extended using SDN and OpenFlow to adapt priorities in-network. Using the eight internal perport queues of a switch, discrete priorities are used to schedule, and additionally adapt, the priorities on the switch. This approach could give the opportunity for priority-based routing by using the SDN-controller for routing decisions and configuring the switches. The evaluation of this thesis is done by simulating NCSs and emulating the network containing the middlebox. For this, a simulation of an inverted pendulum is implemented for which the use of DPDK is compared to standard sockets. It can be shown that DPDK is able to perform better due to less delay and jitter. The scheduling application is evaluated by comparing it to a round-robin scheduling approach. The result suggests that the application is able to keep multiple NCS more stable than it’s round-robin counterpart. Furthermore, it is able to stabilize a more unstable system faster and more effectively. While the maximum sampling time for a system with a pendulum having an initial angle of 35° was found to be 50ms for the round-robin scheme, the middlebox is able to keep the system stable until 120ms. The application using OpenFlow is evaluated with respect to the time it takes to configure the switch as well as the overhead imposed by the configuration compared to the number of NCS within the network.Item Open Access Regularizing gradient properties on deep neural networks(2016) Wallkötter, SebastianThis bachelor thesis presents a novel approach to training deep neural networks. While back propagating on these deep architectures, it is often found that the gradient vanishes. Further, layers with logistic activation functions will saturate from top to bottom, which is slowing down convergence as the gradient can't propagate well past these saturated layers. Both observations awaken the wish to have the ability to regularize the gradient and directly force its properties. This thesis enables such regularization by modifying the network's cost function. Such changes modify the classic back propagation equations and therefore, the new extended back propagation equations are computed. Finally, two methods of regularization and their combination are presented and tested on a binary and a multi-class (MNIST) classification problem to show the benefits of training with these methods. A result of this thesis is the finding that this setup massively improves training on logistic networks, on the one hand enabling otherwise impossible classification in the multi-class case, while on the other speeding up training on a single class.