2,415 research outputs found

    Distributed Web Service Coordination for Collaboration Applications and Biological Workflows

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    In this dissertation work, we have investigated the main research thrust of decentralized coordination of workflows over web services. To address distributed workflow coordination, first we have developed ā€œWeb Coordination Bondsā€ as a capable set of dependency modeling primitives that enable each web service to manage its own dependencies. Web bond primitives are as powerful as extended Petri nets and have sufficient modeling and expressive capabilities to model workflow dependencies. We have designed and prototyped our ā€œWeb Service Coordination Management Middlewareā€ (WSCMM) system that enhances current web services infrastructure to accommodate web bond enabled web services. Finally, based on core concepts of web coordination bonds and WSCMM, we have developed the ā€œBondFlowā€ system that allows easy configuration distributed coordination of workflows. The footprint of the BonFlow runtime is 24KB and the additional third party software packages, SOAP client and XML parser, account for 115KB

    On the Use of Queueing Petri Nets for Modeling and Performance Analysis of Distributed Systems

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    Predictive performance models are used increasingly throughout the phases of the software engineering lifecycle of distributed systems. However, as systems grow in size and complex-ity, building models that accurately capture the different aspects of their behavior becomes a more and more challenging task. The challenge stems from the limited model expressivenes

    Performance Testing of Distributed Component Architectures

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    Performance characteristics, such as response time, throughput andscalability, are key quality attributes of distributed applications. Current practice,however, rarely applies systematic techniques to evaluate performance characteristics.We argue that evaluation of performance is particularly crucial in early developmentstages, when important architectural choices are made. At first glance, thiscontradicts the use of testing techniques, which are usually applied towards the endof a project. In this chapter, we assume that many distributed systems are builtwith middleware technologies, such as the Java 2 Enterprise Edition (J2EE) or theCommon Object Request Broker Architecture (CORBA). These provide servicesand facilities whose implementations are available when architectures are defined.We also note that it is the middleware functionality, such as transaction and persistenceservices, remote communication primitives and threading policy primitives,that dominates distributed system performance. Drawing on these observations, thischapter presents a novel approach to performance testing of distributed applications.We propose to derive application-specific test cases from architecture designs so thatthe performance of a distributed application can be tested based on the middlewaresoftware at early stages of a development process. We report empirical results thatsupport the viability of the approach

    Second Workshop on Modelling of Objects, Components and Agents

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    This report contains the proceedings of the workshop Modelling of Objects, Components, and Agents (MOCA'02), August 26-27, 2002.The workshop is organized by the 'Coloured Petri Net' Group at the University of Aarhus, Denmark and the 'Theoretical Foundations of Computer Science' Group at the University of Hamburg, Germany. The homepage of the workshop is: http://www.daimi.au.dk/CPnets/workshop02

    Modelling- and Simulation-Based Design of Multi-tier Systems

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    This paper introduces a domain-specific language for modelling andsimulation-based design of multi-tier systems. Ā Multi-tier systems are complexand very few general models have been developed. Rather, models are alwaysdedicated to a specific architecture. Our approach allows for rapidexperimentation with different multi-tier alternatives. Not only parameters,but also structure can be drastically varied. Ā Using graph transformation,multi-tier systems models are translated into Queueing Petri Nets (QPNs) in asystematic way for analysis with the SimQPN simulator. Ā We describe QPN, ourmulti-tier architecture visual language, as well as the transformation between them. Ā A case study demonstrates the power of the approach for design-space exploration

    Modelling- and Simulation-Based Design of Multi-tier Systems

    Get PDF
    This paper introduces a domain-specific language for modelling andsimulation-based design of multi-tier systems. Ā Multi-tier systems are complexand very few general models have been developed. Rather, models are alwaysdedicated to a specific architecture. Our approach allows for rapidexperimentation with different multi-tier alternatives. Not only parameters,but also structure can be drastically varied. Ā Using graph transformation,multi-tier systems models are translated into Queueing Petri Nets (QPNs) in asystematic way for analysis with the SimQPN simulator. Ā We describe QPN, ourmulti-tier architecture visual language, as well as the transformation between them. Ā A case study demonstrates the power of the approach for design-space exploration

    Performance Analysis of Live-Virtual-Constructive and Distributed Virtual Simulations: Defining Requirements in Terms of Temporal Consistency

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    This research extends the knowledge of live-virtual-constructive (LVC) and distributed virtual simulations (DVS) through a detailed analysis and characterization of their underlying computing architecture. LVCs are characterized as a set of asynchronous simulation applications each serving as both producers and consumers of shared state data. In terms of data aging characteristics, LVCs are found to be first-order linear systems. System performance is quantified via two opposing factors; the consistency of the distributed state space, and the response time or interaction quality of the autonomous simulation applications. A framework is developed that defines temporal data consistency requirements such that the objectives of the simulation are satisfied. Additionally, to develop simulations that reliably execute in real-time and accurately model hierarchical systems, two real-time design patterns are developed: a tailored version of the model-view-controller architecture pattern along with a companion Component pattern. Together they provide a basis for hierarchical simulation models, graphical displays, and network I/O in a real-time environment. For both LVCs and DVSs the relationship between consistency and interactivity is established by mapping threads created by a simulation application to factors that control both interactivity and shared state consistency throughout a distributed environment
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