Universität Stuttgart
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Item Open Access Development and analysis of a window manager concept for consolidated 3D rendering on an embedded platform(2015) Zhao, HanNowadays with the information technology rapidly developing, an increasing number of 2D and 3D graphics are used in automotive displaying systems, to provide vehicle information, driving assistance, etc. With the demand of 3D models interacting with each other, an implementation should have a 3D compositing capability. However, traditional 2D compositing implementations are not capable of 3D models compositing tasks. In order to composite 3D graphics on embedded platform, the 3D compositing implementation is necessary. Therefore, a concept of window manager is developed aiming to composite 3D graphics with an optimized efficiency for embedded platform. Specially for automotive platforms, a virtualization is made to unify multiple Electronic Control Units (ECUs) into one single ECU platform. On this platform, a server and multiple clients are implemented with dedicated Virtual Machines (VMs). The server is in charge of rendering tasks requested from clients. Based on this, a 3D compositing concept is implemented. It handles efficiently the multiple 3D applications situation using a method of off-screen rendering. A server-side virtualization is also implemented by replacing certain client-side commands during commands forwarding. With this virtualization implementation, multiple applications run simultaneously with accessing single 3D GPU only. Moreover, due to this implementation, monolithic rendering operations affecting all applications, e.g. uniform lighting operation, are possible.Item Open Access Design and implementation of a domain specific language for defining ECM workloads in elastic cloud environments using TOSCA(2015) Kukhtichev, SergeyEach year the volume of the content produced by enterprises increases by 35%-50%. Most of this information is stored by companies as unstructured data. Organizations implement Enterprise Content Management (ECM) to structure content and to mitigate legal risks. ECM includes strategies and tools for increasing the effectiveness of content management. Using the right ECM components is one of the factors for successful implementation of ECM. There is a gap between business customers who implement ECM strategies and ECM architects and cloud providers, who create and deploy ECM solutions. On the one side, there are no generally accepted terms, which precisely describe the ECM domain. Different developers of the ECM systems could use the same name for ECM components, which implement different functionality, or they could use different names for ECM components with similar functionality. On the other side, each customer has unique workloads for Enterprise Content Management. ECM architects have to define these workloads and deploy an ECM solution that will fulfill the customer's requirements. The goal of the Thesis is to develop a DSL for ECM domain, which will be understandable by business customers, ECM architects and cloud providers. The language should define terms and workloads that are related to the ECM domain. The business customers should be able to create a description of the requirements to ECM solution using a language that they understand. The ECM architect should be able to define the ECM related terms and associated workloads from the customer's description, design a topology, and publish it in a specialized catalog. The cloud provider should be able to map the high level topology to the exact infrastructure.Item Open Access Packet scheduling algorithms for a software-defined manufacturing environment(2015) Roy Chowdhury, SujataWith the vision of Industry 4.0, Internet of things (IoT) and Internet of Services (IoS) are making their way to the modern manufacturing systems and industrial automation. As a consequence, modern day manufacturing systems need wider product variation and customization to meet the customer's demands and survive in the competitive markets. Traditional, dedicated systems like assembly lines cannot adapt the rapidly changing requirement of today's manufacturing industries. A flexible and highly scalable infrastructure is needed to support such systems. However, most of the applications in manufacturing systems require strict QoS guarantees. For instance, time-sensitive networks like in industrial automation and smart factories need hard real-time guarantees. Deterministic networks with bounded delay and jitter are essential requirement for such systems. To support such systems, non-deterministic queueing delay has to be eliminated from the network. To this end, we present Time-Sensitive Software-Defined Networks (TSSDN) with a logically centralized controller which computes transmission schedules based on the global view of the network. SDN control logic computes optimized transmission schedules for the end hosts to avoid in network queueing delay. To compute transmission schedules, we present Integer Linear Programming and Routing and Scheduling Algorithms with heuristics that schedule and route unicast and multicast flows. Our evaluations show that it is possible to compute near optimal transmission schedules for TSSDN and bound network delays and jitter.Item Open Access Supporting multi-tenancy in Relational Database Management Systems for OLTP-style software as a service applications(2015) Schiller, Oliver; Mitschang, Bernhard (Prof. Dr.-Ing. habil.)The consolidation of multiple tenants onto a single relational database management system (RDBMS) instance, commonly referred to as multi-tenancy, turned out being beneficial since it supports improving the profit margin of the provider and allows lowering service fees, by what the service attracts more tenants. So far, existing solutions create the required multi-tenancy support on top of a traditional RDBMS implementation, i. e., they implement data isolation between tenants, per-tenant customization and further tenant-centric data management features in application logic. This is complex, error-prone and often reimplements efforts the RDBMS already offers. Moreover, this approach disables some optimization opportunities in the RDBMS and represents a conceptual misstep with Separation of Concerns in mind. For the points mentioned, an RDBMS that provides support for the development and operation of a multi-tenant software as a service (SaaS) offering is compelling. In this thesis, we contribute to a multi-tenant RDBMS for OLTP-style SaaS applications by extending a traditional disk-oriented RDBMS architecture with multi-tenancy support. For this purpose, we primarily extend an RDBMS by introducing tenants as first-class database objects and establishing tenant contexts to isolate tenants logically. Using these extensions, we address tenant-aware schema management, for which we present a schema inheritance concept that is tailored to the needs of multi-tenant SaaS applications. Thereafter, we evaluate different storage concepts to store a tenant’s tuples with respect to their scalability. Next, we contribute an architecture of a multi-tenant RDBMS cluster for OLTP-style SaaS applications. At that, we focus on a partitioning solution which is aligned to tenants and allows obtaining independently manageable pieces. To balance load in the proposed cluster architecture, we present a live database migration approach, whose design favors low migration overhead and provides minimal interruption of service.Item Open Access Position sharing for location privacy in non-trusted systems(2015) Skvortsov, Pavel; Rothermel, Kurt (Prof. Dr. rer. nat. Dr. h.c.)Currently, many location-aware applications are available for mobile users of location-based services. Applications such as Google Now, Trace4You or FourSquare are being widely used in various environments where privacy is a critical issue for users. A general solution for preserving location privacy for a user is to degrade the quality of his or her position information. In this work, we propose an approach that uses spatial obfuscation to secure the users’ position information. By revealing the user’s position with a certain degree of obfuscation, the first crucial issue is the tradeoff between privacy and precision. This tradeoff problem is caused by limited trust in the location service providers: higher obfuscation increases privacy but leads to lower quality of service. We overcome this problem by introducing the position sharing approach. Our main idea is that position information is distributed amongst multiple providers in the form of separate data pieces called position shares. Our approach allows for the usage of non-trusted providers and flexibly manages the user’s location privacy level based on probabilistic privacy metrics. In this work, we present the multi-provider based position sharing approach, which includes algorithms for the generation of position shares and share fusion algorithms. The second challenge that must be addressed is that the user’s environmental context can significantly decrease the level of obfuscation. For example, a plane, a boat and a car create different requirements for the obfuscated region. Therefore, it is very important to consider map-awareness in selecting the obfuscated areas. We assume that a static map is known to an adversary, which may help in deriving the user’s true position. We analyze both how map-awareness affects the generation and fusion of position shares and the difference between the map-aware position sharing approach and its open space based version. Our security analysis shows that the proposed position sharing approach provides good security guarantees for both open space and constrained space based models. The third challenge is that multiple location servers and/or their providers may have different trustworthiness from the user’s point of view. In this case, the user would prefer not to reveal an equal level (precision) of position information to every server. We propose a placement optimization approach that ensures that risk is balanced among the location servers according to their individual trust levels. Our evaluation shows significant improvement of privacy guarantees after applying the optimized share distribution, in comparison with the equal share distribution. The fourth related problem is the location update algorithm. A high number of different location servers n (corresponding to n privacy levels) may lead to significant communication overhead. Each update would require n messages from the mobile user to the location servers, especially in cases of high update rate. Therefore, we propose an optimized location update algorithm to decrease the number of messages sent without reducing the number of privacy levels and the user’s privacy.Item Open Access Distributed graph processing and partitioning for spatiotemporal queries in the context of camera networks(2015) Maaß, SteffenThis work presents a scalable, distributed architecture for processing spatiotemporal queries in the context of camera networks based on a graph structure. With the ever-increasing presence of cameras and the emergence of camera-networks, e.g., in the context of campus security, it becomes increasingly important to provide a robust and scalable architecture to store and retrieve detected events. In this work a distributed graph processing engine will be presented which is well suited for read and write tasks in the environment of spatiotemporal image-similarity based workloads. The key ideas presented in this work are the architecture of a scalable graph processing system well-suited for processing spatio-temporal queries and the design of a distributed and robust vertex-partitioning strategy for the graph which is being defined by the spatiotemporal attributes of the stored events. The work will show multiple lightweight heuristics for partitioning the graph among the nodes participating in the system, focusing on load-balancing between workers and high edge-locality for vertices. The system and the partitioning strategies will be evaluated, showing that the system scales with the number of workers and the problem size and is able to answer proportionally more queries per second. It will also be shown that the lightweight heuristics for partitioning the graph produce a relatively good balancing of the vertices on the worker-nodes and can be executed in an online-fashion, resulting in similar performance when compared to a traditional hash-partitioning while providing far superior edge-locality.Item Open Access Optimal routing for networked control systems using OpenFlow(2015) Bach, Ha DuyNetworked Control System (NCS), which implements a feedback control loop over a communication network connecting sensors, actuators and controller, has gained a significance demand. However, in many cases, the infrastructure is not previously designed for dedicated control network because of the cost or because of the technology vision. Therefore, NCS should utilize the popular IP networks, which often do not provide any QoS provision. This is a challenge as NCS are sensitive toward delay and loss. In this thesis, I want to revisit a previous study on NCS, as well as to look at the measurement of delay in previous literature and current market devices. After that, I will point out the challenges of implementing NCS services of the previous study in real switches supporting SDN technology. Finally, I propose a solution on the most popular platform of SDN technology and demonstrate my evaluation.Item Open Access Physikalisches Schlussfolgern: Monte Carlo Methoden zur Inferenz physikalischer Situationen(2015) Vetter, TobiasDie vorliegende Bachelorarbeit gliedert sich in die beiden Teile Theoretische Grundlagen und Praktische Ausführung. In ersterem werden die Grundlagen des Rejection Sampling und des Markov-Chain-Monte-Carlo Verfahrens erläutert, die anschließend im zweiten Teil zur Lösung des vorliegenden Problems Anwendung finden, welches in der Stabilisierung eines physikalischen Körpers im Raum besteht. Um die Effizienz der Algorithmen angemessen bewerten zu können, werden mehrere Versuche mit variierenden Parametern durchgeführt. Die Versuchsergebnisse werden anschließend ausgewertet, analysiert und visualisiert.Item Open Access Design and implementation of TOSCA Service Templates for provisioning and executing bone simulation in cloud environments(2015) Dehghanipour, MarziehRecent years have shown an increasing trend to move applications and services into cloud infrastructures. Cloud-based applications typically consist of distributed components which are connected and communicate with each other. Automating the deployment and management of these components is one of the major challenges in IT world. The OASIS TOSCA standard provides a meta-model for describing the structure of composite cloud-based applications, which provides automation for deployment and management of these applications. TOSCA-based applications may be executed via the OpenTOSCA (a run-time environment for TOSCA-based applications) environment, which has been developed by the University of Stuttgart. Simulation applications deal with heterogeneous and huge data sources. Adequate data management and data provisioning for these applications are some of the most significant challenges for simulation applications. SIMPL is a framework which provides a generic approach for data management and data provisioning in simulation applications. SIMPL frees users to deal with any low-level details of data sources and corresponding data management operations. Both the TOSCA standard and the SIMPL framework are based on workflows. The first goal of this master's thesis is to combine the TOSCA standard with the SIMPL framework in order to enable the generic data provisioning and data management approach offered by SIMPL as an integral part of the TOSCA standard. A further and main part of this work is to design and implement TOSCA Service Templates for provisioning and executing bone simulations in cloud environments. Different variants of a TOSCA Service Template realizing a bone simulation in a cloud-native way have to be developed and implemented. In other words, a SaaS solution for PANDAS bone simulation is provided in the scope of this master's thesis with the help of TOSCA and SIMPL technologies.Item Open Access Distributed stream processing in a global sensor grid for scientific simulations(2015) Benzing, Andreas; Rothermel, Kurt (Prof. Dr. rer. nat)With today's large number of sensors available all around the globe, an enormous amount of measurements has become available for integration into applications. Especially scientific simulations of environmental phenomena can greatly benefit from detailed information about the physical world. The problem with integrating data from sensors to simulations is to automate the monitoring of geographical regions for interesting data and the provision of continuous data streams from identified regions. Current simulation setups use hard coded information about sensors or even manual data transfer using external memory to bring data from sensors to simulations. This solution is very robust, but adding new sensors to a simulation requires manual setup of the sensor interaction and changing the source code of the simulation, therefore incurring extremely high cost. Manual transmission allows an operator to drop obvious outliers but prohibits real-time operation due to the long delay between measurement and simulation. For more generic applications that operate on sensor data, these problems have been partially solved by approaches that decouple the sensing from the application, thereby allowing for the automation of the sensing process. However, these solutions focus on small scale wireless sensor networks rather than the global scale and therefore optimize for the lifetime of these networks instead of providing high-resolution data streams. In order to provide sensor data for scientific simulations, two tasks are required: i) continuous monitoring of sensors to trigger simulations and ii) high-resolution measurement streams of the simulated area during the simulation. Since a simulation is not aware of the deployed sensors, the sensing interface must work without an explicit specification of individual sensors. Instead, the interface must work only on the geographical region, sensor type, and the resolution used by the simulation. The challenges in these tasks are to efficiently identify relevant sensors from the large number of sources around the globe, to detect when the current measurements are of relevance, and to scale data stream distribution to a potentially large number of simulations. Furthermore, the process must adapt to complex network structures and dynamic network conditions as found in the Internet. The Global Sensor Grid (GSG) presented in this thesis attempts to close this gap by approaching three core problems: First, a distributed aggregation scheme has been developed which allows for the monitoring of geographic areas for sensor data of interest. The reuse of partial aggregates thereby ensures highly efficient operation and alleviates the sensor sources from individually providing numerous clients with measurements. Second, the distribution of data streams at different resolutions is achieved by using a network of brokers which preprocess raw measurements to provide the requested data. The load of high-resolution streams is thereby spread across all brokers in the GSG to achieve scalability. Third, the network usage is actively minimized by adapting to the structure of the underlying network. This optimization enables the reduction of redundant data transfers on physical links and a dynamic modification of the data streams to react to changing load situations.