Publish/Subscribe (in short pub/sub) allows clients that share common interest communicate in an asynchronous and loosely-coupled fashion. This paradigm is adopted by many distributed event-driven applications such as social networking services, distributed business processes and cyber-physical systems. These applications cannot afford to have the underlying pub/sub substrate perform unreliably, permanently fail or behave arbitrarily as it will cause significant disturbance to stably serving many end-users. Therefore, a research effort on making pub/sub systems resilient against various failures to sustain high quality of service to the clients is imperative. In this thesis, we focus on the overlay of pub/sub brokers that are widely adopted as a popular architecture for large-scale pub/sub systems. Broker overlays can suffer from various issues such as degradation of topology quality, brokers causing transient or permanent benign failures and Byzantine brokers behaving arbitrarily. We aim to make novel research contributions by exploring fundamental techniques that can help the broker overlays maintain functional and non-functional requirements even under the presence of the aforementioned failures and necessary administrative updates. We first build a set of overlay adaptation primitives that re-configure topologies such as shifting links and replicating brokers. These primitives are designed to involve a small local group of brokers in the pub/sub overlays so that the disruption during the execution of large-scale and dynamic changes can be controlled in a fined-grained manner. For the problem of degrading topology quality, automated planning systems are developed to find a sequence of adaptations that would cause minimal disruption to running services. Also, our primitives can be executed on demand to quickly fail-over a crashed broker or off-load congested brokers. In addition, these on-demand primitives can be used to form a group of dynamically replicated brokers that enforce a novel safety measure to prevent Byzantine brokers from sabotaging the pub/sub overlays. Our contributions are evaluated with systematic consideration of various trade-offs between functional and non-functional properties.

Thesis (M.C.S.)--Carleton University, 2001. / Includes bibliographical references (p. 87). Also available in electronic format on the Internet.

ALMEIDA JÚNIOR, Antenor Teixeira. Espaços e atratores: estratégias de categorização na emergência de interferências sobre a conceitualização de violência. 2013. 184f. – Tese (Doutorado) – Universidade Federal do Ceará, Departamento de Letras Vernáculas, Programa de Pós-graduação em Linguística, Fortaleza (CE), 2013. / Submitted by Márcia Araújo (marcia_m_bezerra@yahoo.com.br) on 2016-01-19T18:35:33Z No. of bitstreams: 1 2013_tese_atajunior.pdf: 2885641 bytes, checksum: 4f0fc10c7ba0f795d9a6a874f8c74b94 (MD5) / Approved for entry into archive by Márcia Araújo(marcia_m_bezerra@yahoo.com.br) on 2016-01-20T10:53:28Z (GMT) No. of bitstreams: 1 2013_tese_atajunior.pdf: 2885641 bytes, checksum: 4f0fc10c7ba0f795d9a6a874f8c74b94 (MD5) / Made available in DSpace on 2016-01-20T10:53:28Z (GMT). No. of bitstreams: 1 2013_tese_atajunior.pdf: 2885641 bytes, checksum: 4f0fc10c7ba0f795d9a6a874f8c74b94 (MD5) Previous issue date: 2013 / In this research, I analyzed the characteristics and mechanisms that make categorization, as a cognitive process, a Complex Adaptive System and the strategies of categorization that work in the emergency of inferences for the conceptualization of the category VIOLENCE and subcategory URBAN VIOLENCE. The theoretical support for the investigation of the research aims are the assumptions of the paradigm of chaos, complexity and complex systems, as outlined by Bertalanffy (1977), Morin (2005), Holland (1995, 1998) and Larsen-Freeman and Cameron ( 2008; 2012), who propose the concepts of systems, complexity, attractors, phase space and characteristics and mechanisms of a Complex Adaptive System. In the case of inferential process, I sought theoretical support in Relevance Theory, as proposed by Sperber and Wilson (1995, 2001), Feltes (1999, 2007), Alves and Gonçalves (2006) and Yus (2008, 2013). To get to the characterization of categorization as a Complex Adaptive System, I considered the properties presented by Holland (1995) and Larsen-Freeman and Cameron (2008), seeking to expand the concept and explain the instability of the categorical system based on the complexity theory (Morin, 1977). For this investigation, based on the complexity theory, it was also necessary to include the concept of system, phase space and attractors so relevant to the methodological approach used in this research. Such a procedure resulted in a typology of categorization strategies for the analysis and explanation of how the various feasible spaces for the conceptualizing of VIOLENCE are triggered. The category "VIOLENCE" was chosen for analysis in view of its update status in the last twenty years and the various researches on the subject carried out by Larsen-Freeman and Cameron, Macedo and Feltes, scholars whose studies served as basis for the methodological proposal of this thesis. In order to verify the research hypotheses, a methodological design which involved intensive direct observation of 33 categorizers was used. The participants answered questionnaires about the categorization of VIOLENCE and participated of verbal protocols to verify the inference mechanisms involved in the process. The analyses result allow for the following conclusions: VIOLENCE categorization has the properties and mechanisms of Complex Adaptive Systems because the systems present, in whole and in parts, variation within a stable range. The categorizers use the inferential process to trigger the attractors that lead to the phase space in which diverse knowledge about violence is available for its conceptualization in a strategic way. / Nesta pesquisa, analisamos as características e mecanismos que tornam a categorização, como processo cognitivo, um Sistema Adaptativo Complexo e as estratégias de categorização que atuam na emergência de inferências para a conceitualização da categoria VIOLÊNCIA e a subcategoria VIOLÊNCIA URBANA. Nosso suporte teórico para a investigação dos nossos objetivos são os pressupostos do paradigma do caos, da complexidade e dos sistemas complexos, conforme delineados por Bertalanffy (1977), Morin (2005), Holland (1995; 1998) e Larsen- Freeman e Cameron (2008; 2012), que propõem os conceitos de sistemas, complexidade, atratores, espaço fase e características e mecanismos de um Sistema Adaptativo Complexo. No caso do processo inferencial, buscamos amparo teórico na Teoria da Relevância, conforme proposta por Sperber e Wilson (1995; 2001), Feltes (1999; 2007), Alves e Gonçalves (2006) e Yus (2008; 2013). Para chegarmos à caracterização da categorização como Sistema Adaptativo Complexo, levamos em consideração as propriedades apresentadas por Holland (1995) e Larsen- Freeman e Cameron (2008), buscando ampliar o conceito e explicar a instabilidade do sistema categorizacional à luz da complexidade (MORIN, 1977). Para essa investigação com base na complexidade foi necessário ainda incluir o conceito de sistema, espaço fase e atratores tão caros à abordagem metodológica utilizada. Esse procedimento resultou em uma tipologia de estratégias de categorização para análise e explicitação de como se aciona os diversos espaços possíveis para conceitualização de VIOLÊNCIA. Escolhemos a categoria VIOLÊNCIA para investigar nosso objetivo tendo em vista a atualização do assunto nos últimos vinte anos e pelos trabalhos com essa categoria realizados por Larsen-Freeman e Cameron, Macedo e Feltes, cujos estudos serviram de base para nossa proposta metodológica. Para verificarmos nossas hipóteses, utilizamos como desenho metodológico uma pesquisa com observação direta e intensiva de 33 categorizadores que responderam a questionários sobre a categorização de VIOLÊNCIA e participaram de protocolos verbais para verificação dos mecanismos de inferenciação. Os resultados das análises permitem as seguintes conclusões: a categorização de VIOLÊNCIA possui propriedades e mecanismos dos Sistemas Adaptativos Complexos, pois os sistemas apresentam no todo e nas partes, variedade dentro de uma estabilidade. Os categorizadores utilizam o processo inferencial para acionar os atratores que levam ao espaço fase em que se encontram diversos conhecimentos sobre violência para sua conceitualização de forma estratégica.

Septima Conferencia Iberoamericana de Complejidad, Informatica y Cibernetica, CICIC 2017 - 7th Ibero-American Conference on Complexity, Informatics and Cybernetics, CICIC 2017; Orlando; United States; 21 March 2017 through 24 March 2017; Code 131437 / Adaptive learning systems constitute a new approach to e-learning systems, they allow adapting the content to the individual characteristics of students. Two of its main components are the domain model and the student model, whose key elements are the learning objects (OA) and learning style, respectively. LOs are digital educational content provided by the course while learning style will define how the student learns. Within this context the motivation of this study is to propose a partnership model for relating the LOs with student learning styles. After conducting a systematic review of previous work related a mathematical model of partnership LOs and learning styles by reference to their type of format and content type to determine which is associated LOs better student learning style is presented.

Yes / Purpose: The aim of this research is to evaluate if the Complex Adaptive Systems theory can be used to explain resilience strategies within the pharmaceutical supply chain Research Approach: An in depth review of literature surrounding resilience in the pharmaceutical supply chain. In order to pursue this study agenda, data was collected from Scopus, the largest peer review journal as well as EBSCOhost. The PRISMA guideline was adopted in the systematic review process where 34 peer reviewed papers in the field of CAS, supply chain and supply chain resilience were identified with respect to methodologies employed, location of the study and approaches. Findings and Originality: The systematic review of literature shows that there are inherent similarities between the concept of resilience and the CAS theory. The CAS theory explains that PSC’s are dynamic, have emergent behaviours complex, adaptive, interconnected as well as possess schemas that regulate their operations. Hence if resilience strategies are to be employed to mitigate disruptive events they need to be harnessed in a manner to fit this particular supply chain. This work is innovative as it provides a new insight into the contemporary discourse on resilience strategy creation and deployment, examining the use of this theory in the PSC, and thus provides original contribution. Research Impact: This study contributes to the existing literature base, by providing theoretical underpinnings in the area of resilience and the pharmaceutical supply chain. This furthers the CAS agenda, SCR agenda and also presents an innovative output which warrants more detailed analysis and feasibility testing. Practical Impact: Complexity principles are multi-scaled and multi-domain and as such the suggestions put forward in this theoretical framework can be adopted in various supply chain networks as well as disruptive events. It provides new insights with regards to structures for managers seeking to design and improve resilience supply chains, a key element of which is the adoption of a holistic analysis by SC managers when developing resilience strategies. This is critical if disruptions are to be identified and mitigated before their impact is felt.

No / Self-adaptive systems are evolving systems that can adjust their behaviour to accommodate dynamic requirements or to better serve the goal. These systems can vary in their architecture, operation, or adaptive strategies based on the application. Moreover, the evaluation can happen in different ways depending on system architecture and its requirements. Self-adaptive systems can be prone to situations like adaptation faults, inconsistencies in context or low performance on tasks due to their dynamism and complexity. That is why it is important to have reliability assurance of the system to monitor such situations which can compromise the system functionality. In this paper, we provide a brief background on different types of self-adaptive systems and various ways a system can evolve. We discuss the different mechanisms that have been applied in the last two decades for reliability evaluation of such systems and identify challenges and limitations as research opportunities related to the self-adaptive system’s reliability evaluation. / This research was undertaken as a part of the “Model-based Reliability Evaluation for Autonomous Systems with Evolving Architectures” project funded by the University of Bradford under the SURE Grant scheme.

Yes / Changes in world-wide population trends have provided new demands for new technologies in areas such as care and rehabilitation. Recent developments in the the field of robotics for neurorehabilitation have shown a range of evidence regarding usefulness of these technologies as a tool to augment traditional physiotherapy. Part of the appeal for these technologies is the possibility to place a rehabilitative tool in one’s home, providing a chance for more frequent and accessible technologies for empowering individuals to be in charge of their therapy. this manuscript introduces the Supervised Care and Rehabilitation Involving Personal Tele-robotics (SCRIPT) project. The main goal is to demonstrate design and development steps involved in a complex intervention, while examining feasibility of using an instrumented orthotic device for home-based rehabilitation after stroke. Methods: the project uses a user-centred design methodology to develop a hand/wrist rehabilitation device for home-based therapy after stroke. The patient benefits from a dedicated user interface that allows them to receive feedback on exercise as well as communicating with the health-care professional. The health-care professional is able to use a dedicated interface to send/receive communications and remote-manage patient’s exercise routine using provided performance benchmarks. Patients were involved in a feasibility study (n=23) and were instructed to use the device and its interactive games for 180 min per week, around 30 min per day, for a period of 6 weeks, with a 2-months follow up. At the time of this study, only 12 of these patients have finished their 6 weeks trial plus 2 months follow up evaluation. Results: with the “use feasibility” as objective, our results indicate 2 patients dropping out due to technical difficulty or lack of personal interests to continue. Our frequency of use results indicate that on average, patients used the SCRIPT1 device around 14 min of self-administered therapy a day. The group average for the system usability scale was around 69% supporting system usability. Conclusions: based on the preliminary results, it is evident that stroke patients were able to use the system in their homes. An average of 14 min a day engagement mediated via three interactive games is promising, given the chronic stage of stroke. During the 2nd year of the project, 6 additional games with more functional relevance in their interaction have been designed to allow for a more variant context for interaction with the system, thus hoping to positively influence the exercise duration. The system usability was tested and provided supporting evidence for this parameter. Additional improvements to the system are planned based on formative feedback throughout the project and during the evaluations. These include a new orthosis that allows a more active control of the amount of assistance and resistance provided, thus aiming to provide a more challenging interaction. / This work has been partially funded under Grant FP7-ICT-288698(SCRIPT) of the European Community Seventh Framework Programme.

No description available.

The relaxation of international boundaries has enabled the globalisation of markets making available an ever increasing number of specialised suppliers and markets. Inevitably this results in supply chains sharing suppliers and customers reflected in a network of relationships. Within this context firms buyers configure their supply relationships based on their perception of supply risk. Risk is managed by either increasing trust or commitment or by increasing the number of suppliers. Increasing trust and commitment facilitates collaboration and reduces the propensity for a supplier to exit the relationship. Conversely, increasing the number of suppliers reduces dependency and increases the ease of making alternative supply arrangements. The emergent network of relationships is dynamic and complex, and due in no small part to the influence of inventory management practices, tightly coupled. This critical organization of the network describes a system that contrary to existing supply chain conceptualisation exists far from equilibrium, requiring a different more appropriate theoretical lens through which to view them. This thesis adopts a Complex Adaptive Systems (CAS) perspective to position supply networks as tightly coupled complex systems which according to Normal Accident Theory (NAT) are vulnerable to disruptions as a consequence of normal operations. The consequential boundless and emergent nature of supply networks makes them difficult to research using traditional empirical methods, instead this research builds a generalised supply network agent based computer model, allowing network constituents (agents) to take autonomous parallel action reflecting the true emergent nature of supply networks. This thesis uses the results from a series of carefully designed computer experiments to elucidate how supply networks respond to a variety of market structures and permitted agent behaviours. Market structures define the vertical (between tier) and horizontal (within tier) levels of price differentiation. Within each structure agents are permitted to autonomously modify their prices (constrained by market structure) and collaborate by sharing demand information. By examining how supply networks respond to different permitted agent behaviours in a range of market structures this thesis makes 4 contributions. Firstly, it extends NAT by incorporating the adaptive nature of supply network constituents. Secondly it extends supply chain management by specifying supply networks as dynamic not static phenomena. Thirdly it extends supply chain risk management through developing an understanding of the impact different permitted behaviour combinations on the networks vulnerability to disruptions in the context of normal operations. Finally by developing the understanding how normal operations impact a supply networks vulnerability to disruptions it informs the practice of supply chain risk management.

Software-intensive systems are increasingly expected to operate under changing and uncertain conditions, including not only varying user needs and workloads, but also fluctuating resource capacity. Self-adaptation is an approach that aims to address this problem, giving systems the ability to change their behavior and structure to adapt to changes in themselves and their operating environment without human intervention. Self-adaptive systems tend to be reactive and myopic, adapting in response to changes without anticipating what the subsequent adaptation needs will be. Adapting reactively can result in inefficiencies due to the system performing a suboptimal sequence of adaptations. Furthermore, some adaptation tactics—atomic adaptation actions that leave the system in a consistent state—have latency and take some time to produce their effect. In that case, reactive adaptation causes the system to lag behind environment changes. What is worse, a long running adaptation action may prevent the system from performing other adaptations until it completes, further limiting its ability to effectively deal with the environment changes. To address these limitations and improve the effectiveness of self-adaptation, we present proactive latency-aware adaptation, an approach that considers the timing of adaptation (i) leveraging predictions of the near future state of the environment to adapt proactively; (ii) considering the latency of adaptation tactics when deciding how to adapt; and (iii) executing tactics concurrently. We have developed three different solution approaches embodying these principles. One is based on probabilistic model checking, making it inherently able to deal with the stochastic behavior of the environment, and guaranteeing optimal adaptation choices over a finite decision horizon. The second approach uses stochastic dynamic programming to make adaptation decisions, and thanks to performing part of the computations required to make those decisions off-line, it achieves a speedup of an order of magnitude over the first solution approach without compromising optimality. A third solution approach makes adaptation decisions based on repertoires of adaptation strategies— predefined compositions of adaptation tactics. This approach is more scalable than the other two because the solution space is smaller, allowing an adaptive system to reap some of the benefits of proactive latency-aware adaptation even if the number of ways in which it could adapt is too large for the other approaches to consider all these possibilities. We evaluate the approach using two different classes of systems with different adaptation goals, and different repertoires of adaptation strategies. One of them is a web system, with the adaptation goal of utility maximization. The other is a cyberphysical system operating in a hostile environment. In that system, self-adaptation must not only maximize the reward gained, but also keep the probability of surviving a mission above a threshold. In both cases, our results show that proactive latency-aware adaptation improves the effectiveness of self-adaptation with respect to reactive time-agnostic adaptation.