Model Based Development of Quality-Aware Software Services

Modelling languages and development frameworks give support for functional and structural description of software architectures. But quality-aware applications require languages which allow expressing QoS as a first-class concept during architecture design and service composition, and to extend existing tools and infrastructures adding support for modelling, evaluating, managing and monitoring QoS aspects. In addition to its functional behaviour and internal structure, the developer of each service must consider the fulfilment of its quality requirements. If the service is flexible, the output quality depends both on input quality and available resources (e.g., amounts of CPU execution time and memory). From the software engineering point of view, modelling of quality-aware requirements and architectures require modelling support for the description of quality concepts, support for the analysis of quality properties (e.g. model checking and consistencies of quality constraints, assembly of quality), tool support for the transition from quality requirements to quality-aware architectures, and from quality-aware architecture to service run-time infrastructures. Quality management in run-time service infrastructures must give support for handling quality concepts dynamically. QoS-aware modeling frameworks and QoS-aware runtime management infrastructures require a common evolution to get their integration

An introduction to Quality of Security Services

We examine the concept of security as a dimension of Quality of Service in distributed systems. We provide a discussion and examples of user- specified security variables and show how the range of service levels associated with these variables can support the provision of Quality of Security Service. We also discuss various design implications regarding security ranges provided in a QoS-aware distributed system. Our goal has been to provide an understanding of QoSS and variant security, and to determine whether these concepts can be useful in improving security service and system performance in QoS-aware distributed systems. We described the general requirements for system attributes to participate in the provision of Quality of Service, and described how certain security attributes might meet these requirements. We then described various forms of user and application security "ranges "and showed how these ranges can make sense in relation to existing security policies, when those ranges are presented as user choices. Finally we described security ranges as forming a coherent system of relationships in a distributed multi-tiered system. Our conclusion is that it may be possible for security to be a semantically meaningful dimension of Quality of Service without compromising existing security policies. Further study is needed to understand the effectiveness of QoSS in improving system performance in QoS-aware systems.Approved for public release; distribution is unlimited

Low Cost - High Performance Streaming Server Architecture Making Use of Multiple Operating Systems

University of Tokyo (東京大学

Metric-based Selection of Timer Methods for Accurate Measurements

ABSTRACT Performance measurements are often concerned with accurate recording of timing values, which requires timer methods of high quality. Evaluating the quality of a given timer method or performance counter involves analysing several properties, such as accuracy, invocation cost and timer stability. These properties are metrics with platform-dependent values, and ranking and selecting timer methods requires comparisons using multidimensional metric sets, which make the comparisons ambiguous and unnecessary complex. To solve this problem, this paper proposes a new unified metric that allows for a simpler comparison. The one-dimensional metric is designed to capture fine-granular differences between timer methods, and normalises accuracy and other quality attributes by using CPU cycles instead of time units. The proposed metric is evaluated on all timer methods provided by Java and .NET platform APIs

Cooperative framework for open real-time systems

Actualmente, os sistemas embebidos estão presentes em toda a parte. Embora grande parte da população que os utiliza não tenha a noção da sua presença, na realidade, se repentinamente estes sistemas deixassem de existir, a sociedade iria sentir a sua falta. A sua utilização massiva deve-se ao facto de estarem practicamente incorporados em quase os todos dispositivos electrónicos de consumo, telecomunicações, automação industrial e automóvel. Influenciada por este crescimento, a comunidade científica foi confrontada com novos problemas distribuídos por vários domínios científicos, dos quais são destacados a gestão da qualidade de serviço e gestão de recursos - domínio encarregue de resolver problemas relacionados com a alocação óptima de recursos físicos, tais como rede, memória e CPU. Existe na literatura um vasto conjunto de modelos que propõem soluções para vários problemas apresentados no contexto destes domínios científicos. No entanto, não é possível encontrar modelos que lidem com a gestão de recursos em ambientes de execução cooperativos e abertos com restrições temporais utilizando coligações entre diferentes nós, de forma a satisfazer os requisitos não funcionais das aplicações. Devido ao facto de estes sistemas serem dinâmicos por natureza, apresentam a característica de não ser possível conhecer, a priori, a quantidade de recursos necessários que uma aplicação irá requerer do sistema no qual irá ser executada. Este conhecimento só é adquirido aquando da execução da aplicação. De modo a garantir uma gestão eficiente dos recursos disponíveis, em sistemas que apresentam um grande dinamismo na execução de tarefas com e sem restrições temporais, é necessário garantir dois aspectos fundamentais. O primeiro está relacionado com a obtenção de garantias na execução de tarefas de tempo-real. Estas devem sempre ser executadas dentro da janela temporal requirida. O segundo aspecto refere a necessidade de garantir que todos os recursos necessários à execução das tarefas são fornecidos, com o objectivo de manter os níveis de performance quer das aplicações, quer do próprio sistema. Tendo em conta os dois aspectos acima mencionados, o projecto CooperatES foi especificado com o objectivo de permitir a dispositivos com poucos recursos uma execução colectiva de serviços com os seus vizinhos, de modo a cumprir com as complexas restrições de qualidade de serviço impostas pelos utilizadores ou pelas aplicações. Decorrendo no contexto do projecto CooperatES, o trabalho resultante desta tese tem como principal objectivo avaliar a practicabilidade dos conceitos principais propostos no âmbito do projecto. O trabalho em causa implicou a escolha e análise de uma plataforma, a análise de requisitos, a implementação e avaliação de uma framework que permite a execução cooperativa de aplicações e serviços que apresentem requisitos de qualidade de serviço. Do trabalho desenvolvido resultaram as seguintes contribuições: Análise das plataformas de código aberto que possam ser utilizadas na implementação dos conceitos relacionados com o projecto CooperatES; Critérios que influenciaram a escolha da plataforma Android e um estudo focado na análise da plataforma sob uma perspectiva de sistemas de tempo-real; Experiências na implementação dos conceitos do projecto na plataforma Android; Avaliação da practicabilidade dos conceitos propostos no projecto CooperatES; Proposta de extensões que permitam incorporar características de sistemas de tempo real abertos na plataforma Android.Embedded devices are reaching a point where society does not notice its presence; however, if suddenly taken away, everyone would notice their absence. The new, small, embedded devices used in consumer electronics, telecommunication, industrial automation, or automotive systems are the reason for their massive spread. Influenced by this growth and pervasiveness, the scientific community is faced with new challenges in several domains. Of these, important ones are the management of the quality of the provided services and the management of the underlying resources - both interconnected to solve the problem of optimal allocation of physical resources (namely CPU, memory and network as examples), whilst providing the best possible quality to users. Although several models have been presented in literature, a recent proposal handles resource management by using coalitions of nodes in open real-time cooperative environments, as a solution to guarantee that the application’s non-functional requirements are met, and to provide the best possible quality of service to users. This proposal, the CooperatES framework, provides better models and mechanisms to handle resource management in open real-time systems, allowing resource constrained devices to collectively execute services with their neighbours, in order to fulfil the complex Quality of Service constraints imposed by users and applications. Within the context of the CooperatES framework, the work presented in this thesis evaluates the feasibility of the implementation of the framework’s Quality of Service concept within current embedded Java platforms, and proposes a solution and architecture for a specific platform: the Android operating system. To this purpose, the work provides an evaluation of the suitability of Java solutions for real-time and embedded systems, an evaluation of the Android platform for open real-time systems, as well as discusses the required extensions to Android allowing it to be used within real-time system. Furthermore, this thesis presents a prototype implementation of the CooperatES framework within the Android platform, which allows determining the suitability of the proposed platform extensions for open real-time systems applications