A maioria das organizações depende atualmente de algum tipo de infraestrutura computacional para suportar as atividades críticas para o negócio. Esta dependência cresce com o aumento da capacidade dos sistemas informáticos e da confiança que se pode depositar nesses sistemas, ao mesmo tempo que aumenta também o seu tamanho e complexidade. Os sistemas transacionais, tipicamente centrados em bases de dados utilizadas para armazenar e gerir a informação de suporte às tarefas diárias, sofrem naturalmente deste mesmo problema. Assim, uma solução frequentemente utilizada para amenizar a dificuldade em lidar com a complexidade dos sistemas passa por delegar sob outras organizações o trabalho de desenvolvimento, ou mesmo por utilizar soluções já disponíveis no mercado (sejam elas proprietárias ou abertas). A diversidade de software e componentes alternativos disponíveis atualmente torna necessária a existência de testes padronizados que ajudem na seleção da opção mais adequada entre as alternativas existentes, considerando uma conjunto de diferentes características. No entanto, o sucesso da investigação em testes padronizados de desempenho e confiabilidade contrasta radicalmente com os avanços em testes padronizados de segurança, os quais têm sido pouco investigados, apesar da sua extrema relevância. Esta tese discute o problema da definição de testes padronizados de segurança, comparando-o com outras iniciativas de sucesso, como a definição de testes padronizados de desempenho e de confiabilidade. Com base nesta análise é proposta um modelo de base para a definição de testes padronizados de segurança. Este modelo, aplicável de forma genérica a diversos tipos de sistemas e domínios, define duas etapas principais: qualificação de segurança e teste padronizado de confiança. A qualificação de segurança é um processo que permite avaliar um sistema tendo em conta os aspectos e requisitos de segurança mais evidentes num determinado domínio de aplicação, dividindo os sistemas avaliados entre aceitáveis e não aceitáveis. O teste padronizado de confiança, por outro lado, consiste em avaliar os sistemas considerados aceitáveis de modo a estimar a probabilidade de existirem problemas de segurança ocultados ou difíceis de detectar (o objetivo do processo é lidar com as incertezas inerentes aos aspectos de segurança). O modelo proposto é demonstrado e avaliado no contexto de sistemas transacionais, os quais podem ser divididos em duas partes: a infraestrutura e as aplicações de negócio. Uma vez que cada uma destas partes possui objetivos de segurança distintos, o modelo é utilizado no desenvolvimento de metodologias adequadas para cada uma delas. Primeiro, a tese apresenta um teste padronizado de segurança para infraestruturas de sistemas transacionais, descrevendo e justificando todos os passos e decisões tomadas ao longo do seu desenvolvimento. Este teste foi aplicado a quatro infraestruturas reais, sendo os resultados obtidos cuidadosamente apresentados e analisados. Ainda no contexto das infraestruturas de sistemas transacionais, a tese discute o problema da seleção de componentes de software. Este é um problema complexo uma vez que a avaliação de segurança destas infraestruturas não é exequível antes da sua entrada em funcionamento. A ferramenta proposta, que tem por objetivo ajudar na seleção do software básico para suportar este tipo de infraestrutura, é aplicada na avaliação e análise de sete pacotes de software distintos, todos alternativas tipicamente utilizadas em infraestruturas reais. Finalmente, a tese aborda o problema do desenvolvimento de testes padronizados de confiança para aplicações de negócio, focando especificamente em aplicações Web. Primeiro, é proposta uma abordagem baseada no uso de ferramentas de análise de código, sendo apresentadas as diversas experiências realizadas para avaliar a validade da proposta, incluindo um cenário representativo de situações reais, em que o objetivo passa por selecionar o mais seguro de entre sete alternativas de software para suportar fóruns Web. Com base nas análises realizadas e nas limitações desta proposta, é de seguida definida uma abordagem genérica para a definição de testes padronizados de confiança para aplicações Web. / Most organizations nowadays depend on some kind of computer infrastructure to manage business critical activities. This dependence grows as computer systems become more reliable and useful, but so does the complexity and size of systems. Transactional systems, which are database-centered applications used by most organizations to support daily tasks, are no exception. A typical solution to cope with systems complexity is to delegate the software development task, and to use existing solutions independently developed and maintained (either proprietary or open source). The multiplicity of software and component alternatives available has boosted the interest in suitable benchmarks, able to assist in the selection of the best candidate solutions, concerning several attributes. However, the huge success of performance and dependability benchmarking markedly contrasts with the small advances on security benchmarking, which has only sparsely been studied in the past. his thesis discusses the security benchmarking problem and main characteristics, particularly comparing these with other successful benchmarking initiatives, like performance and dependability benchmarking. Based on this analysis, a general framework for security benchmarking is proposed. This framework, suitable for most types of software systems and application domains, includes two main phases: security qualification and trustworthiness benchmarking. Security qualification is a process designed to evaluate the most obvious and identifiable security aspects of the system, dividing the evaluated targets in acceptable or unacceptable, given the specific security requirements of the application domain. Trustworthiness benchmarking, on the other hand, consists of an evaluation process that is applied over the qualified targets to estimate the probability of the existence of hidden or hard to detect security issues in a system (the main goal is to cope with the uncertainties related to security aspects). The framework is thoroughly demonstrated and evaluated in the context of transactional systems, which can be divided in two parts: the infrastructure and the business applications. As these parts have significantly different security goals, the framework is used to develop methodologies and approaches that fit their specific characteristics. First, the thesis proposes a security benchmark for transactional systems infrastructures and describes, discusses and justifies all the steps of the process. The benchmark is applied to four distinct real infrastructures, and the results of the assessment are thoroughly analyzed. Still in the context of transactional systems infrastructures, the thesis also addresses the problem of the selecting software components. This is complex as evaluating the security of an infrastructure cannot be done before deployment. The proposed tool, aimed at helping in the selection of basic software packages to support the infrastructure, is used to evaluate seven different software packages, representative alternatives for the deployment of real infrastructures. Finally, the thesis discusses the problem of designing trustworthiness benchmarks for business applications, focusing specifically on the case of web applications. First, a benchmarking approach based on static code analysis tools is proposed. Several experiments are presented to evaluate the effectiveness of the proposed metrics, including a representative experiment where the challenge was the selection of the most secure application among a set of seven web forums. Based on the analysis of the limitations of such approach, a generic approach for the definition of trustworthiness benchmarks for web applications is defined.

This article shows the relationship between market and firms through the theory of transactional cost and the relationsthat determine the structure and boundaries of the firm. Using the assumptions from the transactional cost approach,this article proposes some variables that determine optimal organizational structures and their boundaries. / Este artículo muestra la vinculación entre mercado y empresas por medio del enfoque de los costos de transacción, y lasrelaciones que influyen en la determinación de la estructura y los límites de la empresa. Mediante el uso de los supuestosde la teoría de los costos transaccionales, el artículo propone algunas variables que determinan estructuras organizacionalesóptimas y sus respectivos límites.

Orientador: Sandro Rigo / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-13T10:38:16Z (GMT). No. of bitstreams: 1 Kronbauer_FernandoAndre_M.pdf: 3637569 bytes, checksum: 4c5752e2ae7f853d3b5f4971d6d7cbab (MD5) Previous issue date: 2009 / Resumo: Enquanto que arquiteturas paralelas vão se tornando cada vez mais comuns na indústria de computação mais e mais programadores precisam escrever programas paralelos e desta forma são expostos aos problemas relacionados ao uso dos mecanismos tradicionais de controle de concorrência. Memórias transacionais têm sido propostas como um meio de aliviar as dificuldades encontradas ao escreverem-se programas paralelos: o desenvolvedor precisa apenas marcar as seções de código que devem ser executadas de forma atômica e isolada - na forma de transações, e o sistema cuida dos detalhes de sincronização. Neste traba­lho exploramos propostas de memórias transacionais com suporte específico em hardware (HTM), desenvolvendo uma plataforma flexível para a prototipagem, simulação e carac­terização destes sistemas. Também exploramos um sistema de memória transacional com suporte apenas em software (STM), apresentando uma abordagem nova para gerenciar a contenção entre transações. Esta abordagem leva em consideração os padrões de acesso aos diferentes dados de um programa ao escolher o gerenciador de contenção a ser usado para o acesso a estes dados. Elaboramos uma modificação da plataforma de STM que nos permite realizar esta associação entre dados e gerenciamento de contenção, e a partir desta implementação realizamos uma caracterização baseada nos padrões de acesso aos dados de um programa executando em diferentes sistemas de computação. Os resultados de nosso trabalho mostram a viabilidade do uso de memórias transacionais em um ambi­ente de pesquisa acadêmica, e apontam caminhos para a realização de trabalhos futuros que aumentem a viabilidade do seu uso também pela indústria. / Abstract: As parallel architectures become prevalent in the computer industry, more and more programmers are required to write parallel programs and are thus being exposed to the problems related to the use of traditional mechanisms for concurrency control. Transactional memory has been devised as a means for easing the burden of writing parallel Programs: the programmer has only to mark the sections of code that are to be executed in an atomic and isolated way - in the form of transactions, and the system takes care of the synchronization details. In this work we explore different proposals of transactional memories based on specific hardware support (HTM), developing a flexible platform for the prototyping, simulation and characterization of these systems. We also explore a transactional memory system based solely on software support (STM), devising a novel approach for managing the contention among transactions. This new approach takes into account access patterns to different data in an application when choosing the contention management strategy to be used for the access to these data. We made modifications to the STM system in order to enable the association of the data with the contention manager algorithm, and using the new implementation we characterized the STM system based on the access patterns to the data of a program, running it on different hardware. Our results show the viability of the use of transactional memories in an academic environment, and serve as a basis for the proposal of different directions to be followed in future research work, aimed at leveraging the use of transactional memories by the industry. / Mestrado / Mestre em Ciência da Computação

Orientador: Paulo Cesar Centoducatte / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Computação / Made available in DSpace on 2018-08-15T20:59:38Z (GMT). No. of bitstreams: 1 Baldassin_AlexandroJose_D.pdf: 1596141 bytes, checksum: 265aa763c420b69f70d59ff687bd8ad9 (MD5) Previous issue date: 2009 / Resumo: A adoção dos microprocessadores com múltiplos núcleos de execução pela indústria semicondutora tem criado uma crescente necessidade por novas linguagens, metodologias e ferramentas que tornem o desenvolvimento de sistemas concorrentes mais rápido, eficiente e acessível aos programadores de todos os níveis. Uma das principais dificuldades em programação concorrente com memória compartilhada é garantir a correta sincronização do código, evitando assim condições de corrida que podem levar o sistema a um estado inconsistente. A sincronização tem sido tradicionalmente realizada através de métodos baseados em travas, reconhecidos amplamente por serem de difícil uso e pelas anomalias causadas. Um novo mecanismo, conhecido como memória transacional (TM), tem sido alvo de muita pesquisa recentemente e promete simplificar o processo de sincronização, além de possibilitar maior oportunidade para extração de paralelismo e consequente desempenho. O cerne desta tese é formado por três trabalhos desenvolvidos no contexto dos sistemas de memória transacional em software (STM). Primeiramente, apresentamos uma implementação de STM para processadores assimétricos, usando a arquitetura Cell/B.E. como foco. Como principal resultado, constatamos que o uso de sistemas transacionais em arquiteturas assimétricas também é promissor, principalmente pelo fator escalabilidade. No segundo trabalho, adotamos uma abordagem diferente e sugerimos um sistema de STM especialmente voltado para o domínio de jogos computacionais. O principal motivo que nos levou nesta direção é o baixo desempenho das implementações atuais de STM. Um estudo de caso conduzido a partir de um jogo complexo mostra a eficácia do sistema proposto. Finalmente, apresentamos pela primeira vez uma caracterização do consumo de energia de um sistema de STM considerado estado da arte. Além da caracterização, também propomos uma técnica para redução do consumo em casos de alta contenção. Resultados obtidos a partir dessa técnica revelam ganhos de até 87% no consumo de energia / Abstract: The shift towards multicore processors taken by the semiconductor industry has initiated an era in which new languages, methodologies and tools are of paramount importance to the development of efficient concurrent systems that can be built in a timely way by all kinds of programmers. One of the main obstacles faced by programmers when dealing with shared memory programming concerns the use of synchronization mechanisms so as to avoid race conditions that could possibly lead the system to an inconsistent state. Synchronization has been traditionally achieved by means of locks (or variations thereof), widely known by their anomalies and hard-to-get-it-right facets. A new mechanism, known as transactional memory (TM), has recently been the focus of a lot of research and shows potential to simplify code synchronization as well as delivering more parallelism and, therefore, better performance. This thesis presents three works focused on different aspects of software transactional memory (STM) systems. Firstly, we show an STM implementation for asymmetric processors, focusing on the architecture of Cell/B.E. As an important result, we find out that memory transactions are indeed promising for asymmetric architectures, specially due to their scalability. Secondly, we take a different approach to STM implementation by devising a system specially targeted at computer games. The decision was guided by poor performance figures usually seen on current STM implementations. We also conduct a case study using a complex game that effectively shows the system's efficiency. Finally, we present the energy consumption characterization of a state-of-the-art STM for the first time. Based on the observed characterization, we also propose a technique aimed at reducing energy consumption in highly contended scenarios. Our results show that the technique is indeed effective in such cases, improving the energy consumption by up to 87% / Doutorado / Sistemas de Computação / Doutor em Ciência da Computação

The design of microprocessors is undergoing radical changes that affect the performance and reliability of hardware and will have a high impact on software development. Future systems will depend on a deep collaboration between software and hardware to cope with the current and predicted system design challenges. Instead of higher frequencies, the number of processor cores per chip is growing. Eventually, processors will be composed of cores that run at different speeds or support specialized features to accelerate critical portions of an application. Performance improvements of software will only result from increasing parallelism and introducing asymmetric processing. At the same time, substantial enhancements in the energy efficiency of hardware are required to make use of the increasing transistor density. Unfortunately, the downscaling of transistor size and power will degrade the reliability of the hardware, which must be compensated by software. In this thesis, we present new algorithms and tools that exploit speculative and asymmetric execution to address the performance and reliability challenges of multicore architectures. Our solutions facilitate both the assimilation of software to the changing hardware properties as well as the adjustment of hardware to the software it executes. We use speculation based on transactional memory to improve the synchronization of multi-threaded applications. We show that shared memory synchronization must not only be scalable to large numbers of cores but also robust such that it can guarantee progress in the presence of hardware faults. Therefore, we streamline transactional memory for a better throughput and add fault tolerance mechanisms with a reduced overhead by speculating optimistically on an error-free execution. If hardware faults are present, they can manifest either in a single event upset or crashes and misbehavior of threads. We address the former by applying transactions to checkpoint and replicate the state such that threads can correct and continue their execution. The latter is tackled by extending the synchronization such that it can tolerate crashes and misbehavior of other threads. We improve the efficiency of transactional memory by enabling a lightweight thread that always wins conflicts and significantly reduces the overheads. Further performance gains are possible by exploiting the asymmetric properties of applications. We introduce an asymmetric instrumentation of transactional code paths to enable applications to adapt to the underlying hardware. With explicit frequency control of individual cores, we show how applications can expose their possibly asymmetric computing demand and dynamically adjust the hardware to make a more efficient usage of the available resources.

Magister Psychologiae - MPsych / HIV poses considerable social and health challenges in South Africa, particularly among young people aged 15-24. Research indicates a strong link between risky sexual behaviour and alcohol and illicit drugs. In the Western Cape drug-related behaviours is a growing concern among young people because of relatively high prevalence rates of drug abuse, particularly methamphetamine. Previous South African studies have tended to focused on the link between substance use and risky sexual behaviour among commercial sex workers. The theoretical approach of this study is the information motivation behavioural skills model. Participants were selected using non-probability sampling of 279 first year students registered for Psychology I at the University of the Western Cape. This study employed a quantitative research approach using a survey design. Results: Forty-six percent of students do not believe that the use of illicit drugs has an impact on a person's sexual behavior. However, the findings also showed that only 45% of students believed that there was a difference between illicit drug users correctly using condoms when compared to non-users. Data was analysed using descriptive and inferential statistics. Conclusion: Prevention is our best and most effective means of decreasing risk-taking behaviours associated with HIV infection. Information is the first line of intervention that is necessary to reduce risk-taking behaviours; however prevention strategies and interventions of risk-taking behaviours should aim to increase motivation and help young people integrate information in a way that it is personally relatable. This is vital to address the inconsistencies between perceptions of risk and the realities of risk-taking behaviour. / South Africa

This study pertains to the provision of learning support to remote distance learners from the Basarwa and Bakgalagadi communities in Botswana who enrolled for a secondary school-leaving certificate. The purpose of this case study was to document these learners’ perceptions and experiences of learning at a distance and to improve service delivery. The literature on distance learning support emphasises the importance of making learners’ voices audible as these help gauge the efficacy of learning support. The study was informed by an interpretive paradigm using a mixed-methods approach and is underpinned by Holmberg’ theory of conversational learning (2003). Qualitative data methods collection involved semi-structured interviews, journals, document analysis and observations while a questionnaire provided nested quantitative data. Data sets were triangulated and trustworthiness was enhanced by using Atlas.ti® for qualitative analysis and SAS version 8 software to generate percentages. The key findings showed that distance learners exhibited high intrinsic motivation and 72.1% of them were satisfied with the learning support provided. This substantiates that learner motivation remains a key attribute for successful distance learning in any context. However, policy and managerial flaws did frustrate and unintentionally disadvantage these remote distance learners. Despite their adverse circumstances positive perceptions and experiences were exhibited where learners had access to personalised academic and affective support from empathetic tutors. Implications for practice include policy reviews, ODL staff training and adoption of best practice. A needs assessment to establish learner needs, expectations and aspirations is critical for the design and development of relevant learning materials, and for the delivery of quality learning support to enhance the academic experience of remote learners from marginalised communities. Recommendations may be applicable in other underdeveloped distance learning contexts. Topics for further research exploration in learning support, policy and curriculum issues have been suggested. / Thesis (PhD)--University of Pretoria, 2010. / Education Management and Policy Studies / unrestricted

This study is about the comparison of distance and conventional education programs at the University of Pretoria, South Africa. It is assessed in terms of access, delivery modes and output. The purpose is to investigate and to compare the impact of distance and conventional education on the performances of learners in a postgraduate degree program (B.Ed. (Hons) with specialization in Education Management, assessed in terms of access, delivery and output. It explored documents that were both at the macro (Government Policy documents) and macro (University’s / Faculty documents) with the aim of answering the main research question, with other identified sub-research questions that have been raised.: What is the comparison between the impact of distance and conventional education on the performances of learners in a postgraduate BEd (Hons) degree program with specialization in Education Management, when assessed in terms of access, delivery mode and output? A review of relevant literature exposed and compared the essence of both modes of delivery. Data were collected from identified key role players on the program, which included administrators, module coordinators, course presenters, and tutors, some of the students on the program, and some of those that had discontinued their studies with the university. These were done using one-on-one semi-structured and focus group interviews, telephone interviews and questionnaires in order to obtain qualitative and quantitative data. A sample of 127 distance education students, 45 conventional students, 6 module coordinators, 10 course presenters, 4 tutors, 4 administrators, 1 instructional designer and 10 students that had discontinued their studies participated in the investigation. The data collected were analysed through the use descriptive and inferential statistics, and tabulation for the quantitative data, while the computer assisted qualitative data analysis software [CAQDAS] (Atlas.ti) was employed for the analysis of the transcribed interviews. From the data obtained, it was confirmed that there is a myriad of possible factors that may be responsible for the divergences in the performances, throughput and output rates of enrolled students on the BEd (Hons) Education Management, Law and Policy at the University of Pretoria. It was further revealed that South Africa has identified distance education as a tool of redressing past inequalities in higher education, a process, which the university was involved in by starting relevant programs to this end. However, even though equal access is the focus of the country, but it appeared as if little is being said about financially supporting distance education as for instance, there was no financial assistance to distance education students on the program. Due to the incursion of the university into areas, where the impact of university education had not previously being felt, its choice of the mode of delivery was limited to the print, the first generation, which was expected to bring all students on the program at par since all would have access to it. However, despite the efforts made by the university, it was discovered that there existed some gaps between the qualities of the learning experiences, which students from both modes were exposed to. Examples of those identified were lack of designated counseling unit for distance education students, and inadequate number of administrative staff to meet the needs of the ever increasing number of distance education students. However, it appeared that there were no prominent discrepancies that could be found between the two modes, and one could assume that both modes were guided by a similar underpinning philosophy, which drove the ethos of the programs that impacted on the instructional design. It was also found that there were challenges faced by the academic staff involved in the program under investigation, who felt that there might be the need for the institution to demarcate between academe interested in distance education, and those that were not, and the need for the institution to review its stand on rewards and incentives systems for staff involved in distance education. It was believed by them that this would be the way out of the dearth of research presently facing the university on this delivery mode. The study suggests that quality issues especially in relation to an African setting should be looked into, since a large percentage of the students involved in the program were from the rural areas. Finally, the study identified various limitations, and made suggestions for further research, and recommendations for improvement and immediate action. / Thesis (PhD (Curriculum Studies))--University of Pretoria, 2007. / Curriculum Studies / unrestricted

This research is to develop in-basket work samples to measure an individual's willingness and ability to display behaviors that are often associated with successful leadership in organizations as described by Bass.

Tidigare forskning om ledarskap ger en bild av vilken ledarskapsstil som ger bäst resultat för organisationen och mest positiv effekt för följaren. Denna studie undersökte hur några av de vanligaste ledarskapsstilarna, Transformativt, Transaktionellt samt Leader-Member Exchange (LMX), skattades av följarna. Ett formulär med fyra fiktiva chefsbeskrivningar användes för kvantitativ datainsamling, där Transformativt ledarskap och låg nivå av LMX skattades högst. Att låg nivå av LMX skattades högre än hög nivå går mot vad tidigare forskning säger är den bästa approachen sett till prestation för organisationen och följarna. Kulturella skäl till detta motsatta resultat för LMX diskuteras. / The existing research in leadership has explored which style of leadership that generates the best results for the organization and has the most positive effect for the follower. This study looked at some of the most common leadership styles, Transformative, Transactional and Leader-Member Exchange (LMX), and how they were rated by the followers. A form containing four fictitious manager descriptions were used. The result showed that transformative leadership and low level of LMX were rated highest. The fact that low level of LMX was rated higher than high level contradicts existing research claims. Cultural differences are suggested to account for the different rating of LMX in this research.