The business pressures which companies and organisations encounter are steadily growing. They continuously have to improve their efficiency to keep up with these new developments. One very important aspect in doing so is the reinforced adoption of computer based information systems. This paper focuses on a computer based system which is able to automate everyday business communication between distributed team members. Reliable and confidential message delivery, event notification, the integration of different end devices (mobile phones, PCs etc.) and the message transport across different networks (wireless, wired) have been allocated as the main system requirements. Based on these requirements the performance of two middleware technologies, namely CORBA and Web services, has been compared. The result of this comparison was that both technologies are suited to use for implementing such a system but both too, have strengths and weaknesses in achieving the stated requirements. CORBA for example, due to several supporting, already included services, allows the programmer to concentrate on the application development itself and use these services to ensure reliable and confidential message transmission. Additionally, CORBA is very efficient in using the bandwidth of the underlying communication network, but makes higher demands to the memory space available on clients. This is critical, if clients are mobile devices with limited resources. Web service technology is much more modest than CORBA with respect to the client side memory space, but message transmission requires much more bandwidth. Further one there are no built-in security and reliability services available for Web services, like there are for CORBA. Hence it is up the application programmer to manually implement these features; however he has not necessarily develop everything from scratch but can resort to already existing specifications, still having the freedom of developing specially tailored features. In short could be stated that CORBA is more consequential and consistent and WS technology is more adjustable and flexible.

Development of distributed real-time applications, in contrast to best effort applications, traditionally have been a slow process due to the lack of available standards, and the fact that no commercial off the shelf (COTS) distributed object computing (DOC) middleware supporting real-time requirements have been available to use, in order to speed up the development process without sacrificing any quality. Standards and DOC middlewares are now emerging that are addressing key requirements of real-time systems, predictability and efficiency, and therefore, new possibilities such as component decomposition of real-time systems arises. A number of component decomposed architectures of the distributed active real-time database system DeeDS is described and discussed, along with a discussion on the most suitable DOC middleware. DeeDS is suitable for this project since it supports hard real-time requirements and is distributed. The DOC middlewares that are addressed in this project are OMG's Real-Time CORBA, Sun's Enterprise JavaBeans, and Microsoft's COM/DCOM. The discussion to determine the most suitable DOC middleware focuses on real-time requirements, platform support, and whether implementations of these middlewares are available.

The spread of wireless devices inspired the creation of a DEECo component model suitable for designing applications with immanent mobility and dynamic composition where the system architecture emerges at runtime. A great challenge in implementation of such a system is the underlying communication mechanism based on gossip protocol in order to achieve resilience and suitability for MANET networks. In this thesis we propose an optimization of the protocol exploiting infrastructure networks, but still preserving the gossip-like communication without a centralized element. The improvement is based on forming communication groups introduced at the design level. The experiments show a substantial decrease in the number of sent messages and a decrease in time of data delivery. The timing aspect of data delivery is further elaborated for MANET networks by implementing a pulling mechanism with significant improvement of the latency. Part of this thesis is dedicated to a formal specification of the system semantic to provide a precise rationale about its properties and laying the ground for further extensions and research. Powered by TCPDF (www.tcpdf.org)

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22070号 / 工博第4651号 / 新制||工||1725(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 引原 隆士, 教授 土居 伸二, 特定教授 中村 武恒 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The dramatic popularity of graph database has resulted in a growing interest in graph queries. Two major topics are included in graph queries. One is based on structural relationship to find meaningful results, such as subgraph pattern match and shortest-path query. The other one focuses on semantic-based query to find question answering from knowledge bases. However, most of these queries take knowledge graphs as flat forms and use only normal relationship to mine these graphs, which may lead to mistakes in the query results. In this thesis, we find hierarchical relationship in the knowledge on their semantic relations and make use of hierarchical relationship to query on knowledge graphs; and then we propose a meaningful query and its corresponding efficient query algorithm to get top-k answers on hierarchical knowledge graphs. We also design algorithms on distributed frameworks, which can improve its performance. To demonstrate the effectiveness and the efficiency of our algorithms, we use CISCO related products information that we crawled from official websites to do experiments on distributed frameworks.

Inovácia na finančných trhoch poskytuje nové príležitosti. Algoritmické obchodovanie je vhodný spôsob využitia týchto príležitostí. Táto práca sa zaoberá návrhom a implementáciou systému, ktorý by dovoľoval svojím uživateľom vytvárať vlastné obchodovacie stratégie, a pomocou nich obchodovať na burzách. Práca kladie dôraz na návrh distribuovaného systému, ktorý bude škálovatelný, pomocou technológií cloud computingu.

This thesis deals with principles of measuring of acceleration with commercially available accelerometers and theoretical analyses of measuring of angular speed of rotational motion. Then the proposition of application’s connection controlled by microprocessor and software solution with implementation of serial communication interface is described. The function of the apparatus is examined with experimental measuring and elaborated protocol.

This thesis should introduce a reader with basic objectives of parallel computing followed by distributed systems. The thesis is also aimed at description of cryptographic attacks. The main point should be to obtain theoretic information for design of distributed system for cryptoanalysis.

This thesis deals with distributed applications and WCF framework. The first part is based on theoretical information about distributed systems and we also concentrate on models of distributed systems. Next part describes WCF framework and key elements of WCF application. The following chapter is designated to introduce information about prime factorization. Then the knowledge from previous parts is used to create examples of service-oriented applications. In conclusion we discuss main parts of designing distributed application to solve factorization problem. Finally the comparison of distributed and dedicated application is made.

Research in the area of load balancing in distributed systems has not yet come with an optimal load balancing technique. Existing approaches work primarily with replication and sharding. This thesis overviews existing knowledge in this area with focus on shard- ing, and provides an experiment comparing a state-of-the-art load balancing technique called Weighed-Move with a random baseline and an existing domain-specific balancing implementation. As a significant part of the project, we engineered a generic and scal- able load balancer that may be used in any distributed system and deployed it into an existing ad system called Sklik. The major challenges appeared to be tackling various problems related to data consistency, performance and synchronization, together with solving compatibility issues with the rest of the still-evolving ad system. Our experiment shows that the domain-specific load balancing implementation produces data distribution that enables better performance, but Weighed-Move proved to have a great potential and its results are expected to be enhanced by further work on our implementation. 1