Interactions in the style of the ubiquitous computing paradigm are possible today, but only in handcrafted environments within one administrative and technological realm. This thesis describes an architecture (called Continuum), a design that realises the architecture, and a proof-of-concept implementation that brings ubiquitous computing to chaotic environments. Essentially, Continuum enables an ecology at the edge of the network, between users, competing service providers from overlapping administrative domains, competing internet service providers, content providers, and software developers that want to add value to the user experience. Continuum makes the ubiquitous computing functionality orthogonal to other application logic. Existing web applications are augmented for ubiquitous computing with functionality that is dynamically compiled and injected by a middleware proxy into the web pages requested by a web browser at the user?s mobile device. This enables adaptability to environment variability, manageability without user involvement, and expansibility without changes to the mobile. The middleware manipulates self-contained software units with precise functionality (called <i>frames</i>), which help the user interact with contextual services in conjunction with the data to which they are attached. The middleware and frame design explicitly incorporates the possibility of discrepancies between the assumptions of ubiquitous-computing software developers and field realities: multiple administrative domains, unavailable service, unavailable software, and missing contextual information. A framework for discovery and authorisation addresses the chaos inherent to the paradigm through the notion of <i>role assertions</i> acquired dynamically by the user. Each assertion represents service access credentials and contains bootstrapping points for service discovery on behalf of the holding user. A proof-of-concept prototype validates the design, and implements several frames that demonstrate general functionality, including driving discovery queries over multiple service discovery protocols and making equivalences between service types, across discovery protocols.

Data Distribution Service (DDS) specification defines an API for Data-Centric Publish-Subscribe (DCPS) model to achieve efficient data distribution in distributed computing environments. Lack of definition of interoperability architecture in DDS specification obstructs data distribution between different and heterogeneous DDS implementations. In this thesis, DDS is implemented as a CORBA service to achieve interoperability and a QoS policy is proposed for faster data distribution with CORBA features.

Wireless Sensor Networks (WSNs) have become a significant research area in recent years as they play an increasingly important role in bridging the gap between the physical and the virtual world. However, programming wireless sensor networks is extremely challenging. Middleware for WSNs supports the development of sensing-based applications and facilitates programming wireless sensor networks. Middleware is the software that sits in the middle of applications and operating system. There is a large amount of research on middleware development for WSNs. In this thesis, a first attempt is made to simulate mobile agents running on Agilla middleware using a software application. A Java application (Agilla Simulator) is developed and different agents corresponding to various functions are simulated. The performance of the network, namely the time it takes to execute the agents on the simulator is measured. The results of migration delay and reliability in the simulations of different agents are compared with those of the real world experiments. The comparison results presented in the study show that simulations produce results comparable to real life experiments.

With increasing number of applications in Internet and mobile environments, distributed software systems are demanded to be more powerful and flexible, especially in terms of dynamism and security. This dissertation describes my work concerning three aspects: dynamic reconfiguration of component software, security control on middleware applications, and web services dynamic composition. <br><br> Firstly, I proposed a technology named Routing Based Workflow (RBW) to model the execution and management of collaborative components and realize temporary binding for component instances. The temporary binding means component instances are temporarily loaded into a created execution environment to execute their functions, and then are released to their repository after executions. The temporary binding allows to create an idle execution environment for all collaborative components, on which the change operations can be immediately carried out. The changes on execution environment will result in a new collaboration of all involved components, and also greatly simplifies the classical issues arising from dynamic changes, such as consistency preserving etc. <br><br> To demonstrate the feasibility of RBW, I created a dynamic secure middleware system - the Smart Data Server Version 3.0 (SDS3). In SDS3, an open source implementation of CORBA is adopted and modified as the communication infrastructure, and three secure components managed by RBW, are created to enhance the security on the access of deployed applications. SDS3 offers multi-level security control on its applications from strategy control to application-specific detail control. For the management by RBW, the strategy control of SDS3 applications could be dynamically changed by reorganizing the collaboration of the three secure components. <br><br> In addition, I created the Dynamic Services Composer (DSC) based on Apache open source projects, Apache Axis and WSIF. In DSC, RBW is employed to model the interaction and collaboration of web services and to enable the dynamic changes on the flow structure of web services. <br><br> Finally, overall performance tests were made to evaluate the efficiency of the developed RBW and SDS3. The results demonstrated that temporary binding of component instances makes slight impacts on the execution efficiency of components, and the blackout time arising from dynamic changes can be extremely reduced in any applications. / Heutige Softwareanwendungen fuer das Internet und den mobilen Einsatz erfordern bezueglich Funktionalitaet und Sicherheit immer leistungsstaerkere verteilte Softwaresysteme. Diese Dissertation befasst sich mit der dynamischen Rekonfiguration von Komponentensoftware, Sicherheitskontrolle von Middlewareanwendungen und der dynamischen Komposition von Web Services. <br><br> Zuerst wird eine Routing Based Workflow (RBW) Technologie vorgestellt, welche die Ausfuehrung und das Management von kollaborierenden Komponenten modelliert, sowie fuer die Realisierung einer temporaeren Anbindung von Komponenteninstanzen zustaendig ist. D.h., Komponenteninstanzen werden zur Ausfuehrung ihrer Funktionalitaet temporaer in eine geschaffene Ausfuehrungsumgebung geladen und nach Beendigung wieder freigegeben. Die temporaere Anbindung erlaubt das Erstellen einer Ausfuehrungsumgebung, in der Rekonfigurationen unmittelbar vollzogen werden koennen. Aenderungen der Ausfuehrungsumgebung haben neue Kollaborations-Beziehungen der Komponenten zufolge und vereinfachen stark die Schwierigkeiten wie z.B. Konsistenzerhaltung, die mit dynamischen Aenderungen verbunden sind. <br><br> Um die Durchfuehrbarkeit von RBW zu demonstrieren, wurde ein dynamisches, sicheres Middleware System erstellt - der Smart Data Server, Version 3 (SDS3). Bei SDS3 kommt eine Open Source Softwareimplementierung von CORBA zum Einsatz, die modifiziert als Kommunikationsinfrasturkutur genutzt wird. Zudem wurden drei Sicherheitskomponenten erstellt, die von RBW verwaltet werden und die Sicherheit beim Zugriff auf die eingesetzten Anwendungen erhoehen. SDS3 bietet den Anwendungen Sicherheitskontrollfunktionen auf verschiedenen Ebenen, angefangen von einer Strategiekontrolle bis zu anwendungsspezifischen Kontrollfunktionen. Mittels RBW kann die Strategiekontrolle des SDS3 dynamisch durch Reorganisation von Kollabortions-Beziehungen zwischen den Sicherheitskomponenten angepasst werden. <br><br> Neben diesem System wurde der Dynamic Service Composer (DSC) implementiert, welcher auf den Apache Open Source Projekten Apache Axis und WSIF basiert. Im DSC wird RBW eingesetzt, um die Interaktion und Zusammenarbeit von Web Services zu modellieren sowie dynamische Aenderungen der Flussstruktur von Web Services zu ermoeglichen. <br><br> Nach der Implementierung wurden Performance-Tests bezueglich RBW und SDS3 durchgefuehrt. Die Ergebnisse der Tests zeigen, dass eine temporaere Anbindung von Komponenteninstanzen nur einen geringen Einfluss auf die Ausfuehrungseffizienz von Komponeten hat. Ausserdem bestaetigen die Testergebnisse, dass die mit der dynamischen Rekonfiguration verbundene Ausfallzeit extrem niedrig ist.

<p>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.</p><p>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.</p><p>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.</p><p>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.</p><p>In short could be stated that CORBA is more consequential and consistent and WS technology is more adjustable and flexible.</p>

<p>We study techniques to enforce and provision differentiated service levels in <i>Computational Grid</i> systems. The Grid offers simplified provisioning of peak-capacity for applications with computational requirements beyond local machines and clusters, by sharing resources across organizational boundaries. Current systems have focussed on access control, i.e., managing who is allowed to run applications on remote sites. Very little work has been done on providing differentiated service levels for those applications that are admitted. This leads to a number of problems when scheduling jobs in a fair and efficient way. For example, users with a large number of long-running jobs could starve out others, both intentionally and non-intentionally. We investigate the requirements of High Performance Computing (HPC) applications that run in academic Grid systems, and propose two models of service-level management. Our first model is based on global real-time quota enforcement, where projects are granted resource quota, such as CPU hours, across the Grid by a centralized allocation authority. We implement the SweGrid Accounting System to enforce quota allocated by the Swedish National Allocations Committee in the SweGrid production Grid, which connects six Swedish HPC centers. A flexible authorization policy framework allows provisioning and enforcement of two different service levels across the SweGrid clusters; high-priority and low-priority jobs. As a solution to more fine-grained control over service levels we propose and implement a <i>Grid</i> <i>Market </i>system, using a market-based resource allocator called Tycoon. The conclusion of our research is that although the Grid accounting solution offers better service level enforcement support than state-of-the-art production Grid systems, it turned out to be complex to set the resource price and other policies manually, while ensuring fairness and efficiency of the system. Our Grid Market on the other hand sets the price according to the dynamic demand, and it is further incentive compatible, in that the overall system state remains healthy even in the presence of strategic users.</p>

Mobile autonomous robotics in outdoor areas is a challenging task. This domain combines many fields like computer science and electrical engineering. This diploma thesis will show how Miro (Middleware for Robots) has been ported to a new mobile robot platform developed at the Institute for Automation at Chemnitz University of Technology. Additionally, security aspects will be covered, that arise because CORBA is used as middleware, which is an open standard and by default implements no communication security between server and client. Three approaches to solve this problem will be discussed.

Thesis (Ph.D)--Computing, Georgia Institute of Technology, 2009. / Committee Chair: Ling Liu; Committee Member: Brian Cooper; Committee Member: Calton Pu; Committee Member: Douglas Blough; Committee Member: Karsten Schwan. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Delay-tolerant networks (DTNs) are dynamic networks in which senders and receivers are often completely disconnected from each other, often for long periods of time. DTNs are enjoying a burgeoning interest from the research community largely due to the vast potential for meaningful applications, e.g., to enable access to the Internet in remote rural areas, monitor animal behavioral patterns, connect participants in mobile search and rescue applications, provide connectivity in urban environments, and support space communications. Existing work in DTNs generally focuses either on solutions for very specific applications or domains, or on general-purpose protocol-level solutions intended to work across multiple domains. In this proposal, we take a more systems-oriented approach to DTNs. Since applications operating in these dynamic environments would like their connections to be supported by the network technology best suited to the combination of the communication session's requirements and instantaneous network context, we develop a middleware architecture that enables seamless migrations from one communication style to another in response to changing network conditions. We also enable context-awareness in DTNs, using this awareness to adapt communications to more efficiently use network resources. Finally, we explore the systems issues inherent to such a middleware and provide an implementation of it that we test on a mobile computing testbed made up of autonomous robots. / text

Scalable system monitoring is a fundamental abstraction for large-scale networked systems. The goal of this dissertation is to design and build a scalable monitoring middleware that provides system introspection for large distributed systems and that will facilitate the design, development, and deployment of distributed monitoring applications. This middleware will enable monitoring applications to flexibly control the tradeoff between result precision and communication cost and to improve result accuracy in the face of node failures, network delays, and system reconfigurations. We present PRISM (PRecision-Integrated Scalable Monitoring), a scalable monitoring middleware that provides a global aggregate view of large-scale networked systems and that can serve as a building block for a broad range of distributed monitoring applications by coordinating views of multiple vantage points across the network. To coordinate a global view for system introspection, PRISM faces two key challenges: (1) scalability to large systems and high data volumes and (2) safeguarding accuracy in the face of node and network failures. To address these challenges, we design, implement, and evaluate PRISM, a system that defines precision as a new unified abstraction to enable scalable monitoring. PRISM quantifies (im)precision along a three-dimensional vector: arithmetic imprecision (AI) and temporal imprecision (TI) balance precision against monitoring overhead for scalability while network imprecision (NI) addresses the challenge of providing consistency guarantees despite failures. Our prototype implementation of PRISM addresses the challenge of providing these metrics while scaling to a large number of nodes and attributes by (1) leveraging Distributed Hash Tables (DHTs) to create scalable aggregation trees, (2) self-tuning AI budgets across nodes in a principled, near-optimal manner to shift precision to where it is useful, (3) pipelining TI delays across tree levels to maximize batching of updates, and (4) applying dual-tree prefix aggregation which exploits symmetry in our DHT topology to drastically reduce the cost of the active probing needed to maintain NI. Through extensive simulations and experiments on four large-scale testbeds, we observe that PRISM provides a key substrate for scalable monitoring by (1) reducing monitoring load by up to two orders of magnitude compared to existing approaches, (2) providing a flexible framework to control the tradeoff between accuracy, bandwidth cost, and response latency, (3) characterizing and improving confidence in the accuracy of results in the face of system disruptions, and (4) improving the observed accuracy by up to an order of magnitude despite churn. We have built several monitoring applications on top of PRISM including a distributed heavy hitter detection service, a distributed monitoring service for Internet-scale systems, and a detection service for monitoring distributed-denial-of-service (DDoS) attacks at the source-side in distributed networked systems. Finally, we demonstrate how the unified precision abstraction enables new monitoring applications by presenting experiences from these applications. / text