1,721,306 research outputs found
Per-flow Optimal Service Selection for Web Services Based Processes
No full textWith the development of the Service-Oriented Computing (SOC) paradigm, flexible business processes can be defined from independently developed services. Multiple services corresponding to the same functionality but characterized by different Quality of Service (QoS) attributes can be offered by different service providers and the best set of Web services can be selected at run-time in order to maximize the QoS for end users.
In the literature many approaches have been proposed for the optimal service selection which is usually performed on a per-request basis, i.e., considering a single process invocation. In this paper we propose a broker-based framework which solves the optimal service selection on a per-flow basis. Multiple applications, defined as different BPEL processes are considered at the same time and multiple requests to the same process are optimized concurrently.
Service selection is formulated as a constrained non-linear multi-criteria optimization problem and an heuristic algorithm is proposed to determine a scalable and efficient solution.
A comparison with top performing state-of-the-art approaches for a number of different scenarios of interest is also provided. Results show that the overall optimization time reduction which can be achieved by our solution is proportional to the system incoming workload. Order of magnitudes optimization time improvements can be obtained if compared to alternative methods. Moreover, our solution is robust to workload prediction uncertainty
Derivation of Markov Models for Effectiveness Analysis of Adaptable Software Architectures for Mobile Computing
No full textA QoS-based framework for the adaptation of service-based systems
No full textSince a system may require dynamic adaptation for several reasons (e.g., a new version may be available and a new functionality or a different level of quality of service) it should be possible to dynamically adapt a service-based system in an automated manner. In this paper we give a general overview of the main components of a framework, based on an optimization model, that dynamically adapts a service based system (i.e., both the structural and behavioral software and hardware architecture) while minimizing the adaptation costs and guaranteeing a required level of the system qualities. Adaptation actions can be triggered both by a user request and/or automatically after the runtime violation of system quality constraints, or the appearing/disappearing of services into the environment. In this paper we provide also a deeper discussion of the optimization model that is the core of the framework by providing an example of instantiation of the model together with a first experimentation
Modeling and analysis of non-functional properties in component-based systems
No full textAbstractThis paper discusses methodologies for the specification and analysis of performance related properties of components and assemblies of components, and outlines an original approach, called the CB-SPE, for component-based software performance engineering. The proposed approach relies on, and adapts to a CB framework, the concepts and steps of the SPE technology, and uses for modeling the standard RT-UML profile, reshaped according to the CB principles
PRIMA-UML: a Performance Validation Incremental Methodology on Early UML Diagrams
No full textAbstractThe development of complex software systems satisfying performance requirements is achievable only spending careful attention to performance goals throughout the lifecycle, and especially from its very beginning. Unified modeling language (UML) is quickly becoming a standard notation for specification and design of software systems. UML offers several diagrams for separating concerns of different system views, and this feature is helpful to derive early performance models that take into account combined data from these diagrams. In this paper, we introduce a methodology Performance Incremental Validation in UML (PRIMA-UML) aimed at generating a queueing network based performance model from UML diagrams that are usually available early in the software lifecycle. PRIMA-UML is incremental in that it combines information extracted from (and annotated into) different UML diagrams to piecewise build the performance model. Besides, this is not a “black box” approach, as the methodology is open to embed information coming from other UML diagrams (possibly in late lifecycle phases) for detailing, refining or domain tailoring the performance model. This work is a contribute to encompass the performance validation task as an integrated activity within the development process of complex systems. We apply the methodology to a quite simple example to show how effective it can be to get early performance insights
On the relationships between QoS and software adaptability at the architectural level
No full textModern software operates in highly dynamic and often unpredictable environments that can degrade its quality of service. Therefore, it is increasingly important having systems able to adapt their behavior. However, the achievement of software adaptability can influence other software quality attributes, such as availability, performance or cost. This paper proposes an approach for analyzing tradeoffs between the system adaptability and its quality of service. The proposed approach is based on a set of metrics that allow the system adaptability evaluation. The approach can help software architects to guide decisions on system adaptation for fulfilling system quality requirements. The application and effectiveness of the approach are illustrated through examples and a wide set of experiments carried out with a tool we have developed.</p
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