@phdthesis{Rabl2011, author = {Rabl, Tilmann}, title = {Efficiency in Cluster Database Systems - Dynamic and Workload-Aware Scaling and Allocation}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-25821}, school = {Universit{\"a}t Passau}, year = {2011}, abstract = {Database systems have been vital in all forms of data processing for a long time. In recent years, the amount of processed data has been growing dramatically, even in small projects. Nevertheless, database management systems tend to be static in terms of size and performance which makes scaling a difficult and expensive task. Because of performance and especially cost advantages more and more installed systems have a shared nothing cluster architecture. Due to the massive parallelism of the hardware programming paradigms from high performance computing are translated into data processing. Database research struggles to keep up with this trend. A key feature of traditional database systems is to provide transparent access to the stored data. This introduces data dependencies and increases system complexity and inter process communication. Therefore, many developers are exchanging this feature for a better scalability. However, explicitly managing the data distribution and data flow requires a deep understanding of the distributed system and reduces the possibilities for automatic and autonomic optimization. In this thesis we present an approach for database system scaling and allocation that features good scalability although it keeps the data distribution transparent. The first part of this thesis analyzes the challenges and opportunities for self-scaling database management systems in cluster environments. Scalability is a major concern of Internet based applications. Access peaks that overload the application are a financial risk. Therefore, systems are usually configured to be able to process peaks at any given moment. As a result, server systems often have a very low utilization. In distributed systems the efficiency can be increased by adapting the number of nodes to the current workload. We propose a processing model and an architecture that allows efficient self-scaling of cluster database systems. In the second part we consider different allocation approaches. To increase the efficiency we present a workload-aware, query-centric model. The approach is formalized; optimal and heuristic algorithms are presented. The algorithms optimize the data distribution for local query execution and balance the workload according to the query history. We present different query classification schemes for different forms of partitioning. The approach is evaluated for OLTP and OLAP style workloads. It is shown that variants of the approach scale well for both fields of application. The third part of the thesis considers benchmarks for large, adaptive systems. First, we present a data generator for cloud-sized applications. Due to its architecture the data generator can easily be extended and configured. A key feature is the high degree of parallelism that makes linear speedup for arbitrary numbers of nodes possible. To simulate systems with user interaction, we have analyzed a productive online e-learning management system. Based on our findings, we present a model for workload generation that considers the temporal dependency of user interaction.}, subject = {Verteiltes Datenbanksystem}, language = {en} } @phdthesis{Peintner2014, author = {Peintner, Daniel}, title = {Efficient Exchange and Processing of Semi-structured Data in the Embedded Domain}, doi = {10.15475/UPA1113}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-27610}, school = {Universit{\"a}t Passau}, year = {2014}, abstract = {The Internet is a global system of interconnected computers and computer networks where semi-structured data has been successfully applied for exchanging information. In nowadays Internet the huge range of actors, the large diversity of the associated device classes and domains, and the enormous amount of resource-restricted controllers in this system created new requirements and coined also a new term. Internet of Things (IoT), in this regard, refers to identifiable objects (things) and their virtual representations in an Internet-like structure. The fundamental question the thesis tries to answer is whether and how the same semi-structured data can be also applied to the IoT and the embedded domain in spite of resource-limited controllers. In order to discuss this question properties and requirements of embedded networks with regard to the IoT domain have been collected and evaluated. Thereafter the omnipresent semi-structured data exchange format in the Web, the Extensible Markup Language (XML), has been validated. The result was a list of missing requirements such as a compact representation, a representation that can be generated and consumed fast and also allows a small footprint implementation. To address the compiled requirements a binary representation of XML which nowadays is known as W3Cs Efficient XML Interchange (EXI) format has been accomplished which simultaneously optimizes performance and the utilization of computational resources and is designed to be compatible with XML. Moreover, in this work the format has been practically validated and tested. Addressing the needs of the embedded domain one result of this analyzes were optimizations to constrain runtime memory usage and to predict memory growth at runtime. A concept introduced in this thesis is LazyDOM which reduces memory requirements when processing and querying data. By means of a newly proposed code generation technique processing of EXI on ultra-constrained device classes has been enabled and resulting format modifications have been adopted by the W3C standardization. The research work described in this thesis on efficiently exchanging and processing semi-structured data on constrained embedded devices has not only triggered modifications in the W3C EXI format but even is already adopted in domain specific application standards and implementations. The above mentioned optimizations such as predictably limit the memory growth at runtime have been contributed, discussed and evaluated by the W3C experts and become a core part of the EXI specification. Even more significantly from the IoT perspective these optimizations provide the basis for the adoption of this technology in ISO and IEC standardization which is the first time for automotive and power industry to use IoT in the control plane. The implementation of EXI to conduct the evaluation as part of this thesis has become the de-facto open source reference implementation of EXI and became the basis of a number of other reference implementations such as the OpenV2G project that provides the reference implementation of the communication interface in ISO/IEC 15118. In summary the conducted research work has evaluated the options to adapt semi-structured data for the constrained embedded domain, proposed modifications and evaluated those under realistic conditions. This made it relevant for the technology as well as for application standardization despite the short period of this work. As such the research can now be taken as a basis for further challenges in the IoT field namely adopting concepts of the Semantic Web and adapting those to stimulate the quickly expanding eco-system of embedded devices.}, subject = {Mikrocontroller}, language = {en} } @phdthesis{Kaebisch2013, author = {K{\"a}bisch, Sebastian}, title = {Resource Optimization of SOA-Technologies in Embedded Networks}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:739-opus-27338}, school = {Universit{\"a}t Passau}, year = {2013}, abstract = {Embedded networks are fundamental infrastructures of many different kinds of domains, such as home or industrial automation, the automotive industry, and future smart grids. Yet they can be very heterogeneous, containing wired and wireless nodes with different kinds of resources and service capabilities, such as sensing, acting, and processing. Driven by new opportunities and business models, embedded networks will play an ever more important role in the future, interconnecting more and more devices, even from other network domains. Realizing applications for such types of networks, however, is a highly challenging task, since various aspects have to be considered, including communication between a diverse assortment of resource-constrained nodes, such as microcontrollers, as well as flexible node infrastructure. Service Oriented Architecture (SOA) with Web services would perfectly meet these unique characteristics of embedded networks and ease the development of applications. Standardized Web services, however, are based on plain-text XML, which is not suitable for microcontroller-based devices with their very limited resources due to XML's verbosity, its memory and bandwidth usage, as well as its associated significant processing overhead. This thesis presents methods and strategies for realizing efficient XML-based Web service communication in embedded networks by means of binary XML using EXI format. We present a code generation approach to create optimized and dedicated service applications in resource-constrained embedded networks. In so doing, we demonstrate how EXI grammar can be optimally constructed and applied to the Web service and service requester context. In addition, so as to realize an optimized service interaction in embedded networks, we design and develop an optimized filter-enabled service data dissemination that takes into account the individual resource capabilities of the nodes and the connection quality within embedded networks. We show different approaches for efficiently evaluating binary XML data and applying it to resource constrained devices, such as microcontrollers. Furthermore, we will present the effectful placement of binary XML filters in embedded networks with the aim of reducing both, the computational load of constrained nodes and the network traffic. Various evaluation results of V2G applications prove the efficiency of our approach as compared to existing solutions and they also prove the seamless and successful applicability of SOA-based technologies in the microcontroller-based environment.}, subject = {Web Services}, language = {en} }