Fault-tolerant software: dependability/performance trade-offs, concurrency and system support

PhD ThesisAs the use of computer systems becomes more and more widespread in applications that demand high levels of dependability, these applications themselves are growing in complexity in a rapid rate, especially in the areas that require concurrent and distributed computing. Such complex systems are very prone to faults and errors. No matter how rigorously fault avoidance and fault removal techniques are applied, software design faults often remain in systems when they are delivered to the customers. In fact, residual software faults are becoming the significant underlying cause of system failures and the lack of dependability. There is tremendous need for systematic techniques for building dependable software, including the fault tolerance techniques that ensure software-based systems to operate dependably even when potential faults are present. However, although there has been a large amount of research in the area of fault-tolerant software, existing techniques are not yet sufficiently mature as a practical engineering discipline for realistic applications. In particular, they are often inadequate when applied to highly concurrent and distributed software. This thesis develops new techniques for building fault-tolerant software, addresses the problem of achieving high levels of dependability in concurrent and distributed object systems, and studies system-level support for implementing dependable software. Two schemes are developed - the t/(n-l)-VP approach is aimed at increasing software reliability and controlling additional complexity, while the SCOP approach presents an adaptive way of dynamically adjusting software reliability and efficiency aspects. As a more general framework for constructing dependable concurrent and distributed software, the Coordinated Atomic (CA) Action scheme is examined thoroughly. Key properties of CA actions are formalized, conceptual model and mechanisms for handling application level exceptions are devised, and object-based diversity techniques are introduced to cope with potential software faults. These three schemes are evaluated analytically and validated by controlled experiments. System-level support is also addressed with a multi-level system architecture. An architectural pattern for implementing fault-tolerant objects is documented in detail to capture existing solutions and our previous experience. An industrial safety-critical application, the Fault-Tolerant Production Cell, is used as a case study to examine most of the concepts and techniques developed in this research.ESPRIT

Third International Symposium on Space Mission Operations and Ground Data Systems, part 1

Under the theme of 'Opportunities in Ground Data Systems for High Efficiency Operations of Space Missions,' the SpaceOps '94 symposium included presentations of more than 150 technical papers spanning five topic areas: Mission Management, Operations, Data Management, System Development, and Systems Engineering. The papers focus on improvements in the efficiency, effectiveness, productivity, and quality of data acquisition, ground systems, and mission operations. New technology, techniques, methods, and human systems are discussed. Accomplishments are also reported in the application of information systems to improve data retrieval, reporting, and archiving; the management of human factors; the use of telescience and teleoperations; and the design and implementation of logistics support for mission operations

Life-media for a wireless world : participatory democracy and the radio spectrum in Canada and Uruguay

Le spectre radioélectrique est rapidement en train de devenir le médium central, à travers lequel la société communique. Grâce à de multiples facteurs, plusieurs formes de communication, anciennement disparates (la radio, la télévision, la téléphonie mobile, le Wi-Fi) convergent vers la forme éthérée du spectre. L'orientation future de cette convergence dépend largement des acteurs qui sont impliqués dans le design de la réglementation de la communication, ainsi que dans celui des technologies et de leurs usages. Cette thèse doctorale élabore une histoire compréhensive de la communication sans-fil et de sa réglementation, et propose une nouvelle économie politique du spectre, fondée sur la justice sociale. Elle présente, par la suite, une approche épistémologique qui tente de recalibrer les relations entre la société et le spectre radioélectrique. Elle propose que le spectre devra être traité comme une sorte de « média de vie », étant donné qu'il est une composante naturelle de notre environnement et qu'il occupe un rôle central dans notre habilité à exister comme des êtres sociaux communicants. Sa réglementation, alors, devra être sujette au plus haut niveau de participation, de transparence, et d'imputabilité. Cette recherche repose sur une étude de cas internationale et comparative. Elle aborde la capacité des processus de « policymaking » au Canada et en Uruguay à intégrer la participation publique. Elle se fonde sur une documentation extensive et des entretiens avec des législateurs, des régulateurs nationaux et internationaux, des organisations de la société civile, des experts indépendants, des ministères du gouvernement, et des représentants du secteur privé. Des diagnostiques sont établis pour chaque pays et des recommandations politiques concrètes sont faites, qui ne parlent pas seulement des spécificités des politiques du spectre, mais du tissu même de la société démocratique.\ud ______________________________________________________________________________ \ud MOTS-CLÉS DE L’AUTEUR : spectre radioélectrique, politiques de communication, télécommunication, Canada, Urugua

View on 5G Architecture: Version 2.0

The 5G Architecture Working Group as part of the 5GPPP Initiative is looking at capturing novel trends and key technological enablers for the realization of the 5G architecture. It also targets at presenting in a harmonized way the architectural concepts developed in various projects and initiatives (not limited to 5GPPP projects only) so as to provide a consolidated view on the technical directions for the architecture design in the 5G era. The first version of the white paper was released in July 2016, which captured novel trends and key technological enablers for the realization of the 5G architecture vision along with harmonized architectural concepts from 5GPPP Phase 1 projects and initiatives. Capitalizing on the architectural vision and framework set by the first version of the white paper, this Version 2.0 of the white paper presents the latest findings and analyses with a particular focus on the concept evaluations, and accordingly it presents the consolidated overall architecture design

Proceedings of the NASA Conference on Space Telerobotics, volume 4

Papers presented at the NASA Conference on Space Telerobotics are compiled. The theme of the conference was man-machine collaboration in space. The conference provided a forum for researchers and engineers to exchange ideas on the research and development required for the application of telerobotic technology to the space systems planned for the 1990's and beyond. Volume 4 contains papers related to the following subject areas: manipulator control; telemanipulation; flight experiments (systems and simulators); sensor-based planning; robot kinematics, dynamics, and control; robot task planning and assembly; and research activities at the NASA Langley Research Center

Connecting the nation : an historical institutionalist explanation for divergent communications technology outcomes in Canada and Australia

Australia's slow rate of progress in rolling out broadband technologies became a major election issue in 2007, resulting in the National Broadband Network (NBN), the largest public infrastructure investment in Australia's history. Numerous international comparative reports reveal that Australia's lag in the deployment of broadband technologies in relation to Canada, another geographically large, sparsely populated federal system, is significant. Nevertheless, Australia's poor broadband performance is no different than the sluggish adoption of many other forms of electromagnetic communications technologies since the time of the telegraph. This thesis adopts an historical institutionalist approach to explain why Australia trails behind Canada in the take-up of communications technologies. The thesis identifies the different approaches to enabling, coordinating and regulating communications technologies in each country. Importantly, different federal powers for communications technologies have resulted in longstanding differences in the deployment of communications technologies. The Australian government's exclusive powers to legislate for communications technologies resulted in a series of centralised, top-down, single national solutions. Conversely, Canada's decentralised, bottom-up, provincial and municipal solutions approach stems from the provinces' powers to legislate for communications technologies within the provinces. Constitutionally, the Canadian government's powers are for the most part restricted to issues of interconnection between the provinces. Australian policy-makers favour standardised national systems designed to provide equality of service provision which invariably takes longer to deliver services to citizens. While Canada's approach leads to different standards of service provision, the approach is faster in delivering communications technology services to citizens. In explaining why a decentralised approach to deploying communications technologies results in faster take-up of new communications technologies, the concept of varieties of particularism is developed. The term 'varieties of particularism' refers to the unique social, political, economic, technological and geographical peculiarities that exist at the nexus of government, business and communications technologies. These various characteristics differ for each region, jurisdiction, provider and user and present a complex series of challenges for the deployment of new communications technologies. In the broadband era, the traditional monolithic telecommunications carrier model is increasingly obsolete. The research finds that single national solutions designed to meet citizens' communications technology requirements (such as those adopted by Australian policy makers) do not adequately address the varieties of particularism and therefore are slow to be deployed and to be taken-up by citizens. Further, the centralisation of political power in the communication industries prevents many citizens from participating in policy development - a 'build it and they will come' scenario - which neglects the human element of the 'network society'. Consequently, the centralised approach results in policy focused on particular technologies or devices predetermined by government, rather than user functionality which can be delivered by a mix of available technologies. The research finds that Australia's centralised approach discourages innovative uses of available technologies, whereas the Canadian decentralised approach enables citizens to be active policy and network participants where political issues are resolved at the regional or local level. In light of the NBN, the comparison with Canada demonstrates that Australia's centralised approach has important ramifications for future communications technology deployment

Redesigning the United States defense acquisition system

In 1986, the Defense Systems Management College (DSMC) began to examine what defense program managers did as they developed new weapons for the Services. The aim was to determine the tasks program managers performed, how they performed those tasks, what their problems were in doing their work, and what might be done to help them improve their performance. The Interactive Management (IM) methodology developed by Dr. John N. Warfield was chosen as the vehicle for this work. As the workshops provided insights, that knowledge was disseminated throughout the defense acquisition community to provide immediate help to program managers. In 1988, twelve Interactive Management workshops were sponsored by then incumbent Under-Secretaries of Defense, Acquisition (USD[A]) to help them understand acquisition problems and develop ameliorating actions which USD [A] could take to improve the efficiency and effectiveness of the Defense Acquisition System. In June 1991, a series of ten additional workshops began: the first workshop integrated knowledge accumulated from all of the prior workshops to define single set of problems which had been experienced during the process of acquiring defense systems; the second workshop attempted to devise a set of actions which could help resolve those problems. But, by late 1991, it had become apparent that significant improvement in the then current acquisition process would require massive rethinking of the fundamental ideas incorporated within it. In February 1992 a series of workshops was initiated to address acquisition process redesign. These workshops focused on enunciating the specific functions/tasks necessary to develop advanced weapon systems efficiently, and designing a process to accomplish them efficiently and effectively. The acquisition process which emerged from the workshops provided compressed weapon development cycles and reduced the numbers of mandatory oversight and management activities. In turn, those reductions provided the opportunity to incorporate near state of the art technology within newly developed weapons, while at the same time very significantly reducing development cost. The redesigned acquisition process based on the 28 IM workshops was institutionalized by the U. S. Congress in the "Acquisition Streamlining Act of 1994" (Public Law 103- 355). The chapters which follow discuss the: (1) workshops, and insights gained from them; (2) redesigned acquisition process generated; and, potential for broader application of knowledge resulting from this work