2,476 research outputs found

    Knowledge Representation Concepts for Automated SLA Management

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    Outsourcing of complex IT infrastructure to IT service providers has increased substantially during the past years. IT service providers must be able to fulfil their service-quality commitments based upon predefined Service Level Agreements (SLAs) with the service customer. They need to manage, execute and maintain thousands of SLAs for different customers and different types of services, which needs new levels of flexibility and automation not available with the current technology. The complexity of contractual logic in SLAs requires new forms of knowledge representation to automatically draw inferences and execute contractual agreements. A logic-based approach provides several advantages including automated rule chaining allowing for compact knowledge representation as well as flexibility to adapt to rapidly changing business requirements. We suggest adequate logical formalisms for representation and enforcement of SLA rules and describe a proof-of-concept implementation. The article describes selected formalisms of the ContractLog KR and their adequacy for automated SLA management and presents results of experiments to demonstrate flexibility and scalability of the approach.Comment: Paschke, A. and Bichler, M.: Knowledge Representation Concepts for Automated SLA Management, Int. Journal of Decision Support Systems (DSS), submitted 19th March 200

    The Design and Implementation of Real-time Event-based Applications with RTSJ

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    International audienceThis paper presents a framework to design real-time event-based applications using Java. The Real-Time Specification for Java (RTSJ) is well designed for hard periodic real-time systems. Though it also proposes classes to model asynchronous events and deal with sporadic or aperiodic tasks, it remains insufficient. The literature proposes the use of periodic servers called task servers to handle nonperiodic traffics in real-time systems. Unfortunately, there is no support for task servers in RTSJ. In order to fix this lack, we propose an RTSJ extension model. To validate our design, we adapt and implement two policies: the polling server and the deferrable server policies. To show how effi- cient these policies are, we compare implementation results and results obtained with a discrete-event-based simulato

    RTSJ Extensions: Event Manager and Feasibility Analyzer

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    International audienceWe present in this paper our experience on the implementation with RTSJ of advanced algorithms to handle aperiodic traffic. We have adapted existing algorithms in order to take into account some constraints brought about by the use of Java language, and our aim which is to propose a portable mechanism. To circumscribe some difficulties, we had to use some programming ruses which could be better integrated into the specification. From these experiences resulted a set of modifications to the specification which we propose to submit to the community in this paper, in addition to a unified event manager framework

    A Hierarchical Scheduling Model for Dynamic Soft-Realtime System

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    We present a new hierarchical approximation and scheduling approach for applications and tasks with multiple modes on a single processor. Our model allows for a temporal and spatial distribution of the feasibility problem for a variable set of tasks with non-deterministic and fluctuating costs at runtime. In case of overloads an optimal degradation strategy selects one of several application modes or even temporarily deactivates applications. Hence, transient and permanent bottlenecks can be overcome with an optimal system quality, which is dynamically decided. This paper gives the first comprehensive and complete overview of all aspects of our research, including a novel CBS concept to confine entire applications, an evaluation of our system by using a video-on-demand application, an outline for adding further resource dimension, and aspects of our protoype implementation based on RTSJ

    Human machine interface performance and instrumentation for high availability systems

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    Trabalho de projecto de mestrado, Engenharia Informática (Sistemas de Informação), Universidade de Lisboa, Faculdade de Ciências, 2010Air Traffic Control (ATC) provides services whose objective is to manage aircrafts to ensure safely orderly and expeditious flows of traffic. The LISATM system has a number of Controller Working Positions equipped with surveillance display applications, the Operator Display System (ODS). Due to redundancy requirements, there are two equivalent applications developed with different technologies. This project focused on the Air Situation Display System (ASD), na application which provides a surveillance display with user-interaction capability and is developed in Java technology. The application integrates the Radar Fallback keeping the looks and feels from the ODS System, only being developed in a different programming language. Thus the present work focused on monitoring the performance of high availability Real-Time Human-Machine Interface applications. Recommendations were endorsed for quantifiable performance, being these activities accompanied by a corresponding demonstration of results suitability for the intended context. Modules were defined in order to instrument applications Human-Machine Interface High Performance and High Availability (HMI-HPHA) with features necessary and sufficient for the pursuit of Real- Time performance analysis. These modules were developed using JAVA technology using the Java Management eXtensions (JMX), to manage the created agents. All the monitoring services run in real-time so it can inform the managers of changes of the application state as soon as it happens. This implies that the information provided needs to be not only concise but also adequate to the context.O Controle de Tráfego Aéreo (ATC) presta serviços, cujo objectivo é direccionar o fluxo de aeronaves para garantir a ordem, rapidez e segurança do tráfego, bem como para dar informações aos pilotos. O sistema LISATM tem um número de postos de trabalho, para os controladores, equipado com aplicações de vigilância radar (Display System Operator - ODS). Devido a requisitos de redundância, existem duas aplicações equivalentes desenvolvidas com diferentes tecnologias. Este projecto focou-se no Air Display System (ASD). Aplicação que fornece vigilância radar com capacidade de interacção com o utilizador, sendo desenvolvido com tecnologia Java. A aplicação integra o Radar Fallback, mantendo o aspecto e mecânica de utilização igual ao Sistema ODS, com a diferença a residir na linguagem de programação. O foco do presente projecto incidiu sobre o desempenho de aplicações de Interface Homem-Máquina em Tempo-Real de elevada disponibilidade. Desta forma foram elaboradas propostas de recomendações de desempenho quantificáveis a serem incorporadas no ciclo de desenvolvimento de aplicações HMI-HPHA (Human-Machine Interface High Performance and High Availability). Estas foram acompanhadas da correspondente demonstração da adequabilidade ao contexto pretendido. Para isso foram definidos e desenvolvidos módulos de forma a instrumentar a aplicação HMIHPHA com as funcionalidades necessárias e suficientes para a persecução da análise de desempenho. Estes módulos foram desenvolvidos com recurso à tecnologia JAVA e às ferramentas de automatização dos mesmos, usando Java Management eXtensions (JMX) para gerir os agentes desenvolvidos. Todos os serviços de monitoria foram executados em Tempo-Real de modo a informar os gestores aquando de alguma mudança de estado da aplicação. Estas informações necessitam não só de ser concisas, mas também adequadas ao contexto

    A Retrospective Look at the Monitoring and Checking (MaC) Framework

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    The Monitoring and Checking (MaC) project gave rise to a framework for runtime monitoring with respect to formally specified properties, which later came to be known as runtime verification. The project also built a pioneering runtime verification tool, Java-MaC, that was an instantiation of the approach to check properties of Java programs. In this retrospective, we discuss decisions made in the design of the framework and summarize lessons learned in the course of the project

    The jointly scheduling of hard periodic tasks with soft aperiodic events within the Real-Time Specification for Java (RTSJ)

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    The studied problem is the jointly scheduling of hard periodic tasks with soft aperiodic events, where the response times of soft tasks have to be as low as possible while the warranty to meet their deadlines has to be given to hard tasks. A lot of theoretical solutions have been proposed these past two decades but we are interested on the implementability of these solutions under the real-time specification for Java (RTSJ), without changing the scheduler. This led us to adapt the existing algorithms to operate at a user land level in the system, to propose some optimizations and counter measures in order to balance the lost of performances and finally to set up an approximate slack stealer algorithm specifically designed to take into account RTSJ restrictions. We propose new classes to extend the RTSJ API's to implement these mechanisms and some minor modification suggestions to existing ones as a feed back from our RTSJ experiences. We demonstrates the efficiency of the modified algorithms through extensive simulations and the implementability on available RTSJ compliant virtual machine by an overhead measure in real situation with the RTSJ JamaïcaVM from Aïcas. We also measure the overhead on LejosRT, an RTSJ compliant firmware for Lego Mindstorms NXT in development

    Electronic institutions with normative environments for agent-based E-contracting

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    Tese de doutoramento. Engenharia Informática. Faculdade de Engenharia. Universidade do Porto. 201
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