Operating system fault tolerance support for real-time embedded applications

Tese de doutoramento em Electrónica Industrial (ramo de conhecimento em Informática Industrial)Fault tolerance is a means of achieving high dependability for critical and highavailability systems. Despite the efforts to prevent and remove faults during the development of these systems, the application of fault tolerance is usually required because the hardware may fail during system operation and software faults are very hard to eliminate completely. One of the difficulties in implementing fault tolerance techniques is the lack of support from operating systems and middleware. In most fault tolerant projects, the programmer has to develop a fault tolerance implementation for each application. This strong customization makes the fault-tolerant software costly and difficult to implement and maintain. In particular, for small-scale embedded systems, the introduction of fault tolerance techniques may also have impact on their restricted resources, such as processing power and memory size. The purpose of this research is to provide fault tolerance support for real-time applications in small-scale embedded systems. The main approach of this thesis is to develop and integrate a customizable and extendable fault tolerance framework into a real-time operating system, in order to fulfill the needs of a large range of dependable applications. Special attention is taken to allow the coexistence of fault tolerance with real-time constraints. The utilization of the proposed framework features several advantages over ad-hoc implementations, such as simplifying application-level programming and improving the system configurability and maintainability. In addition, this thesis also investigates the application of aspect-oriented techniques to the development of real-time embedded fault-tolerant software. Aspect- Oriented Programming (AOP) is employed to modularize all fault tolerant source code, following the principle of separation of concerns, and to integrate the proposed framework into the operating system. Two case studies are used to evaluate the proposed implementation in terms of performance and resource costs. The results show that the overheads related to the framework application are acceptable and the ones related to the AOP implementation are negligible.Tolerância a falhas é um meio de obter-se alta confiabilidade para sistemas críticos e de elevada disponibilidade. Apesar dos esforços para prevenir e remover falhas durante o desenvolvimento destes sistemas, a aplicação de tolerância a falhas é normalmente necessária, já que o hardware pode falhar durante a operação do sistema e falhas de software são muito difíceis de eliminar completamente. Uma das dificuldades na implementação de técnicas de tolerância a falhas é a falta de suporte por parte dos sistemas operativos e middleware. Na maioria dos projectos tolerantes a falhas, o programador deve desenvolver uma implementação de tolerância a falhas para cada aplicação. Esta elevada adaptação torna o software tolerante a falhas dispendioso e difícil de implementar e manter. Em particular, para sistemas embebidos de pequena escala, a introdução de técnicas de tolerância a falhas pode também ter impacto nos seus restritos recursos, tais como capacidade de processamento e tamanho da memória. O propósito desta tese é prover suporte à tolerância a falhas para aplicações de tempo real em sistemas embebidos de pequena escala. A principal abordagem utilizada nesta tese foi desenvolver e integrar uma framework tolerante a falhas, customizável e extensível, a um sistema operativo de tempo real, a fim de satisfazer às necessidades de uma larga gama de aplicações confiáveis. Especial atenção foi dada para permitir a coexistência de tolerância a falhas com restrições de tempo real. A utilização da framework proposta apresenta diversas vantagens sobre implementações ad-hoc, tais como simplificar a programação a nível da aplicação e melhorar a configurabilidade e a facilidade de manutenção do sistema. Além disto, esta tese também investiga a aplicação de técnicas orientadas a aspectos no desenvolvimento de software tolerante a falhas, embebido e de tempo real. A Programação Orientada a Aspectos (POA) é empregada para segregar em módulos isolados todo o código fonte tolerante a falhas, seguindo o princípio da separação de interesses, e para integrar a framework proposta com o sistema operativo. Dois casos de estudo são utilizados para avaliar a implementação proposta em termos de desempenho e utilização de recursos. Os resultados mostram que os acréscimos de recursos relativos à aplicação da framework são aceitáveis e os relativos à implementação POA são insignificantes

Flexible Scheduling in Middleware for Distributed rate-based real-time applications - Doctoral Dissertation, May 2002

Distributed rate-based real-time systems, such as process control and avionics mission computing systems, have traditionally been scheduled statically. Static scheduling provides assurance of schedulability prior to run-time overhead. However, static scheduling is brittle in the face of unanticipated overload, and treats invocation-to-invocation variations in resource requirements inflexibly. As a consequence, processing resources are often under-utilized in the average case, and the resulting systems are hard to adapt to meet new real-time processing requirements. Dynamic scheduling offers relief from the limitations of static scheduling. However, dynamic scheduling offers relief from the limitations of static scheduling. However, dynamic scheduling often has a high run-time cost because certain decisions are enforced on-line. Furthermore, under conditions of overload tasks can be scheduled dynamically that may never be dispatched, or that upon dispatch would miss their deadlines. We review the implications of these factors on rate-based distributed systems, and posits the necessity to combine static and dynamic approaches to exploit the strengths and compensate for the weakness of either approach in isolation. We present a general hybrid approach to real-time scheduling and dispatching in middleware, that can employ both static and dynamic components. This approach provides (1) feasibility assurance for the most critical tasks, (2) the ability to extend this assurance incrementally to operations in successively lower criticality equivalence classes, (3) the ability to trade off bounds on feasible utilization and dispatching over-head in cases where, for example, execution jitter is a factor or rates are not harmonically related, and (4) overall flexibility to make more optimal use of scarce computing resources and to enforce a wider range of application-specified execution requirements. This approach also meets additional constraints of an increasingly important class of rate-based systems, those with requirements for robust management of real-time performance in the face of rapidly and widely changing operating conditions. To support these requirements, we present a middleware framework that implements the hybrid scheduling and dispatching approach described above, and also provides support for (1) adaptive re-scheduling of operations at run-time and (2) reflective alternation among several scheduling strategies to improve real-time performance in the face of changing operating conditions. Adaptive re-scheduling must be performed whenever operating conditions exceed the ability of the scheduling and dispatching infrastructure to meet the critical real-time requirements of the system under the currently specified rates and execution times of operations. Adaptive re-scheduling relies on the ability to change the rates of execution of at least some operations, and may occur under the control of a higher-level middleware resource manager. Different rates of execution may be specified under different operating conditions, and the number of such possible combinations may be arbitrarily large. Furthermore, adaptive rescheduling may in turn require notification of rate-sensitive application components. It is therefore desirable to handle variations in operating conditions entirely within the scheduling and dispatching infrastructure when possible. A rate-based distributed real-time application, or a higher-level resource manager, could thus fall back on adaptive re-scheduling only when it cannot achieve acceptable real-time performance through self-adaptation. Reflective alternation among scheduling heuristics offers a way to tune real-time performance internally, and we offer foundational support for this approach. In particular, run-time observable information such as that provided by our metrics-feedback framework makes it possible to detect that a given current scheduling heuristic is underperforming the level of service another could provide. Furthermore we present empirical results for our framework in a realistic avionics mission computing environment. This forms the basis for guided adaption. This dissertation makes five contributions in support of flexible and adaptive scheduling and dispatching in middleware. First, we provide a middle scheduling framework that supports arbitrary and fine-grained composition of static/dynamic scheduling, to assure critical timeliness constraints while improving noncritical performance under a range of conditions. Second, we provide a flexible dispatching infrastructure framework composed of fine-grained primitives, and describe how appropriate configurations can be generated automatically based on the output of the scheduling framework. Third, we describe algorithms to reduce the overhead and duration of adaptive rescheduling, based on sorting for rate selection and priority assignment. Fourth, we provide timely and efficient performance information through an optimized metrics-feedback framework, to support higher-level reflection and adaptation decisions. Fifth, we present the results of empirical studies to quantify and evaluate the performance of alternative canonical scheduling heuristics, across a range of load and load jitter conditions. These studies were conducted within an avionics mission computing applications framework running on realistic middleware and embedded hardware. The results obtained from these studies (1) demonstrate the potential benefits of reflective alternation among distinct scheduling heuristics at run-time, and (2) suggest performance factors of interest for future work on adaptive control policies and mechanisms using this framework

A TMO-based Object Group Model to Structuring Replicated Real-Time Objects for Distributed Real-Time Applications

Abstract. We designed the TMO-based Object Group(TMOOG) model with various services for supporting distributed real-time applications, and analyzed whether these given service strategies can be adopted and worked to this model well. In this paper, we are interested in the object group model that can be defined as a single logical view system for providing replication transparency and supporting real-time services. The TMOOG model is based on the concept of the object group recommended by the TINA-C and the OMG. Our model consists of a set of computational Time-triggered and Message-triggered Objects(TMOs) for real-time services and several management objects providing how to manage these TMOs and maintain their information such as repositories for executing given distributed real-time applications. The TMOs in an object group may act as copies, called replicas, of a replicated object with the same roles. For the distributed real-time applications, we focused on the following strategies; dynamic object selection and binding strategy to support replication transparency, and real-time strategy to support real-time applications. For supporting these strategies, we adopted the Dynamic Binder object, the Scheduler object and some related objects to our model. These strategies can be flexibly implemented as object implementations by using appropriate algorithms in the model. Our model is designed on Commercial Off-The-Shelf(COTS) middleware without restricting the special Object Request Broker(ORB) or the operating system. Finally, from the analyzed results numerically, we verified whether our model can support these strategies and showed the feasibility of these service strategies adopted from TMOOG model.

The Evolution of Culture-Climate Interplay in Temporary Multi-Organisations: The Case of Construction Alliancing Projects

Organisational culture has been a long-standing debate in management research. However, in the field of construction project management, it is relatively under-explored. This is mainly due to the different organisational context of Temporary Multi-Organisations (TMOs). This research re-explores the notion of organisational culture in construction projects. Based on Darwin’s theory of evolution this research goes back to the very beginning; illustrating the exact meaning and dynamics of organisational culture in a construction TMO’s ecosystem. This research view an organisation and its forming of culture(s) as part of an evolutionary process. Thus, a critical realist’ view of causation is used as the foundation of the research design and methodology. Case study materials are provided from three Alliancing TMOs belonging to two major infrastructure clients in the UK. A designer culture model and the institutional theory are drawn upon to complement the basis of analysis for evolution. A qualitative research method is employed through semi-structured interviews and pre- and post-interview meetings. Other supporting documentations are also consulted. Three propositions and a postulate are generated and examined against the empirical data. Findings suggest that (i) the TMOs’ culture evolves through a set of recursive stages across the project lifecycle, (ii) the culture of the TMO undergoes several lifecycles during one lifespan of the project, and (iii) there are some evidence that culture at TMO level is learned, rationalised and routinised at corporate level. The postulate shows that it is plausible to predict the trajectory of how a TMO’s culture will evolve across the project lifecycle given a set of organisational features. In practice, findings suggest that hard artifacts alone are not able to sustain established culture throughout the project lifecycle. Awareness is needed to press the “refresh” button at times to maintain the desired culture and manage the evolution path

The alignment of strategic objectives within the context of Temporary Multi-Organisations

Current research investigating the alignment of projects with organisational strategy has predominantly focused on formation and implementation of strategic objectives within the boundary of a single, permanent organisation. Within the construction industry, the temporary organisation, created by the client organisation to deliver the project, is formed from multiple organisations that are brought together, under contractual conditions, to engage in a single endeavour. This creates a situation whereby multiple strategic objectives, and hence, multiple perceptions of project success, are pursued at anyone time. The research, forming this thesis, investigates how the varied organisations that comprise a Temporary Multi-Organisation (TMO) seek to align multiple strategic objectives within the context of a single construction project, and realise project success. In achieving this aim, the study exposes a number of ambiguities and difficulties organisations face when seeking to realise strategic objectives through a TMO. Four cases of recently complete construction projects within the public sector were selected for empirical study. Qualitative data collected from interviews with actors across organisations participating in each TMO, was supported by secondary data comprising of project documentation from each case. The study finds that the strategy of the TMO, which evolves to realise project success, is guided by the varied strategic objectives of organisations participating in the project, and is influenced by the environmental conditions, procurement strategies, client complexity and leadership style of the client project manager, which together, influence the strategic behaviour of the TMO. This research contributes to theories of strategic fit and the theory of temporary organisations through a model of strategic alignment within the context of a TMO that explains the complex interactions, which occur when multiple organisations engage within a single construction project. The research also contributes to the understanding of project success through a model of identifying the varied and competing success criteria within a TMO. Finally, the research contributes to leadership theory, through analysis of leadership styles within the context of a TMO

Geo-Design:

Geo-Design. Advances in bridging geo-information technology and design brings together a wide variety of contributions from authors with backgrounds in urban planning, landscape architecture, education and geo-information technology presenting the latest insights and applications of geodesign. Geo-Design is here understood as a hybridization of the concepts “Geo” – representing the modelling, analytical and visualisation capacities of GIS, and “Design” – representing spatial planning and design, turning existing situations into preferred ones. Through focusing on interdisciplinary design-related concepts and applications of GIS international experts share their recent findings and provide clues for the further development of geodesign. This is important since there is still much to do. Not only in the development of geo-information technology, but especially in bridging the gap with the design disciplines. The uptake on using GIS is still remarkably slow among landscape architects, urban designers and planners, and when utilised it is often restricted to the basic tasks of mapmaking and data access. Knowledge development and dissemination of applications of geodesign through research, publications and education, therefore, remain key factors. This publication draws upon the insights shared at the Geodesign Summit Europe held at the Delft University of Technology in 2014. All contributions in the book are double blind reviewed by experts in the field

Resource sharing platform architecture for an information product factory

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.Page 235 blank.Includes bibliographical references (p. 232-234).Efforts to share resources in collaborative pursuits are hindered by differing data representations, redundant applications, and software incompatibilities. Members of a collaborative effort often span different computational environments and the heterogeneity of contexts disrupts software interoperability. Sharing computational resources has become the focus of many research efforts. Efforts in the 1980s led to the Component Object Model (COM) [Williams, 1998a, 1998b, 1990] and the Common Object Request Broker (CORBA) architectures [Offall et al 1996; OMG, 2003]. In the 1990s both technologies were extended for network support. In recent years, Ian Foster, has phrased the distributed computing problem in terms of sharing computational resources. The grid problem is, "coordinated resource sharing and problem solving in dynamic, multi-institutional virtual organizations", "to support collaborative problem solving in industry, science, and engineering in a data rich environment". [Foster et al, 2001] This work presents a new resource sharing platform architecture for information products that leverages the lessons learned from physical product platforms, the concepts of web services, and grid computing. The platform developed in this thesis integrates the contributions of these three areas into a system that is shown to be more efficient and effective at producing software products.by Abel Sanchez.Ph.D

Assessing the impacts of digital government transformation in the EU

This report presents the results of the conceptual and empirical work conducted as part of the JRC research on “Exploring Digital Government Transformation: understanding public sector innovation in a data-driven society” conducted within the framework of the “European Location Interoperability Solutions for eGovernment (ELISE)" Action of the ISA2 Programme on Interoperability solutions for public administrations, businesses and citizens, coordinated by DIGIT. Building on the systematisation of the state of the art carried out in the previous phase of the research, the report presents an original conceptual framework for assessing the impacts of Digital Government transformation in the EU and discusses the results of case studies carried out using an experimental or quasi-experimental approach to test and validate it, carried out in different policy areas in various EU countries. The report concludes outlining the final proposal of DigiGov F 2.0, which defines the dimensions and elements of analysis for assessing the effects that can be generated by digital innovation in the public sector and the impacts they have at social, economic and political levels in different policy-cycle phases and governance contexts.JRC.B.6-Digital Econom