Universität Stuttgart
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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 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 Erklärung fehlender Ergebnisse bei der Verarbeitung hierarchischer Daten in Spark(2016) Mayer, KarstenEs existieren einige Algorithmen, die Entwicklern bei der Fehlersuche bei einer Datenbankanfrage helfen. Diese Arbeiten beantworten, wieso bestimmte Daten nicht in der Ergebnismenge für eine Anfrage vorhanden sind oder bestimmte nicht erwartete Daten in der Ergebnismenge erscheinen (Why-not-Frage). Für Anfragesprachen, die hierarchische Daten unterstützen, bestehen bisher aber nur wenige Arbeiten. In dieser Arbeit wird untersucht, welche Besonderheiten es für Why-not-Fragen bei hierarchischen Daten gibt. Dazu wird betrachtet, welche besonderen Fragestellungen dafür möglich sind und wie diese geeignet beantwortet werden können. Dabei wird auch ein konkreter Algorithmus für Python entworfen und implementiert. Anhand von diesem kann mit Hilfe eines Beispiels untersucht werden, ob der Algorithmus effizient und effektiv genug ist Why-not-Fragen zu beantworten.Item Open Access Adding value to object storage: integrating analytics with cloud storage back ends(2016) Noori, HodaWith the vast interest of customers in using the cloud infrastructure, cloud providers are going beyond limits to offer advanced functionalities. They try their utmost best to present the services in a way that makes the customers highly attracted and convince them about value and benefits of using such services. For this purpose, cloud providers need to have an access to customers’ data, hence customer-sensitive data stored in repositories should be transferred to the cloud. Object storages are one of the possible solutions for the implementation of repositories in cloud environments. However, due to the data being confidential and fragile, security and encryption mechanisms are required. The application of Enterprise Content Management (ECM) system highly relies on metadata, thus there is a need to keep metadata unencrypted while encrypting data itself. Therefore, cloud providers that are hosting ECM systems are forced to keep metadata unencrypted in order to satisfy the main functionalities of ECM systems on the cloud. Although other cloud providers can offer data encryption and unencrypted metadata as an option to their customers. This leads to the conclusion that enhancing object storages with analysis capabilities in ECM systems is more beneficial if it is done on top of unencrypted metadata. In this thesis I investigate how value can be added to such cloud storage services by only using access the metadata. I specifically focus on providing analytics functionality on metadata. This Master’s thesis aims at providing the means to efficiently analyze the metadata inside a cloud-based ECM system (OSECM) which uses Swift Object Store as its back end repository. I extended the OSECM system with required components by providing new modules that enable the retrieval of metadata from the object storage and the insertion of this metadata into a metadata warehouse. The importance of metadata replication in a distinct data warehouse offers the possibility of benefiting from SQL query capabilities for analysis purposes. Furthermore, an existing tool was integrated as the analysis component to offer the means for interaction with the underlying metadata warehouse and the user interface. Finally, after applying analysis queries, the results are presented on the user interface using the predefined set of visualization interfaces. The supported data structure for the visualization of the result are also defined in this work.Item Open Access Goal-driven context-sensitive production processes : a case study using BPMN(2016) Kar, DebasisThe Fourth Industrial Revolution, also known as Industry 4.0 or Industrial Internet, predicts that Smart Factories driven by Internet of Things (IoT) and Cyber-Physical Systems, will reinvent the traditional manufacturing industry into a digitalized, a context-aware, and an automated manufacturing that will flourish with contemporary Information and Communication Technology (ICT). As the IoT are being deployed across production cites of the manufacturing companies, the need of decision making inside a business process based upon the received contextual data such as employee availability, machine status, etc. from the execution environment has transpired. Production processes need to be updated and optimized frequently to stay competitive in the market. Context-sensitive Adaptive Production Processes is an adept concept that illustrates how a business process can be context-sensitive keeping itself aligned with the abstract organizational goals. The notion of Context-sensitive Adaptive Production Processes leads us to Context-sensitive Execution Step (CES), a logical construct, that encompasses multiple alternative processes, albeit the best-fitting alternative can only be selected, optimized, and executed in runtime. Realization of the context-sensitive business processes requires a model-driven approach. Being Business Process Model and Notation (BPMN) the de-facto standard for business processes modeling, business experts of manufacturing companies can use custom CES construct of BPMN to model and execute context-sensitive business processes in a model-driven approach. This case study is based upon a scenario where there exists multiple alternatives to achieve the same goal in production, nevertheless all the alternatives are not suitable at a certain point of time as changes in business objectives and execution environment makes adaption tougher. Properties of intelligent production processes are different from traditional processes. Such properties along with the scrutinized properties of standard BPMN facilitates modeling CES integrated processes in BPMN. From the requirements inferred from these properties, standard BPMN is extended with extensions such that context-sensitive business processes can be modeled and executed seamlessly. Developed extensions include a new type of process construct and a new type of process definition that are technology agnostic. Thus, CES approach provides a comprehensive solution that makes production processes contextsensitive as well as goal-driven in unison.Item Open Access Feature based volumetric terrain generation(2016) Becher, MichaelTwo-dimensional heightfields are the most common data structure used for storing and rendering of terrain in offline rendering and especially real-time computer graphics. By its very nature, a 2D heightfield cannot store terrain structures with multiple vertical layers such as overhangs and caves. This restriction is lifted if a volumetric data structure is chosen in place of a 2D heightfield. However, the workflow of manual modelling and editing of volumetric terrain usually involves a large number of minor edits and adjustments and is very time consuming. Therefore, I propose to use three-dimensional curve-based primitives to efficiently model prominent, large scale terrain features and present techniques for volumetric generation of a complete terrain surface from the sparse input data by means of diffusion-based algorithms. By combining an efficient, feature-based toolset with a volumetric terrain representation, the modelling workflow is accelerated and simplified while offering the full artistic freedom of volumetric terrain.Item Open Access Realisierung von Balanced Gain and Loss in einem Bose-Hubbard-Modell mit zeitabhängigen Potentialen(2016) Dizdarevic, DanielItem Open Access Contraction Hierarchies für kontinuierliche Graphsimplifizierung mit Qualitätsgarantien(2016) Rupp, TobiasModerne Navigationsdienste können kürzeste Pfade berechnen und diese dann auf Straßenkarten anzeigen. Als zugrunde liegende Datenstruktur für beide Aufgaben kann eine Contraction Hierarchy verwendet werden. Ursprünglich waren Contraction Hierarchies dazu konzipiert, die Suche nach kürzesten Pfaden zu beschleunigen. In dieser Arbeit wurde untersucht, wie sich Contraction Hierarchies aufbauen lassen, sodass sie sich besser für kontinuierlich vereinfachte Darstellungen eignen. Dazu sollten vor allem die groben Straßenverläufe erhalten bleiben und topologische Inkonsistenzen wie Überschneidungen vermieden werden. Diese Anforderungen wurden formalisiert und in heuristischen Vereinfachungsalgorithmen zum Aufbau von Contraction Hierarchies umgesetzt. Für kleine Eingaben wurden mithilfe ganzzahliger linearer Programme garantiert optimale Lösungen berechnet. Damit konnten in empirischen Vergleichen auf dem Deutschlandgraphen Qualitätsgewinne nahe dem Optimum für vereinfachte Darstellungen von Contraction Hierarchies nachgewiesen werden. Außerdem mussten keine längeren Berechnungszeiten für kürzeste Pfade hingenommen werden.Item Open Access Automated calibration for numerical models of riverflow(2016) Fernández, BetsaidaCalibration of numerical models is fundamental since the beginning of all types of hydro system modeling, to approximate the parameters that can mimic the overall system behavior. Thus, an assessment of different deterministic and stochastic optimization methods is undertaken to compare their robustness, computational feasibility, and global search capacity. Also, the uncertainty of the most suitable methods is analyzed. These optimization methods minimize the objective function that comprises synthetic measurements and simulated data. Synthetic measurement data replace the observed data set to guarantee an existing parameter solution. The input data for the objective function derivate from a hydro-morphological dynamics numerical model which represents an 180-degree bend channel. The hydro- morphological numerical model shows a high level of ill-posedness in the mathematical problem. The minimization of the objective function by different candidate methods for optimization indicates a failure in some of the gradient-based methods as Newton Conjugated and BFGS. Others reveal partial convergence, such as Nelder-Mead, Polak und Ribieri, L-BFGS-B, Truncated Newton Conjugated, and Trust-Region Newton Conjugated Gradient. Further ones indicate parameter solutions that range outside the physical limits, such as Levenberg-Marquardt and LeastSquareRoot. Moreover, there is a significant computational demand for genetic optimization methods, such as Differential Evolution and Basin-Hopping, as well as for Brute Force methods. The Deterministic Sequential Least Square Programming and the scholastic Bayes Inference theory methods present the optimal optimization results.