Adaptive Service Composition in Flexible Processes
ABSTRACT In advanced service oriented systems, complex applications, described as abstract business processes, can be executed by invoking a number of available Web services. End users can specify different preferences and constraints and service selection can be performed dynamically identifying the best set of services available at runtime. In this paper, we introduce a new modeling approach to the Web service selection problem that is particularly effective for large processes and when QoS constraints are severe. In the model, the Web service selection problem is formalized as a mixed integer linear programming problem, loops peeling is adopted in the optimization, and constraints posed by stateful Web services are considered. Moreover, negotiation techniques are exploited to identify a feasible solution of the problem, if one does not exist. Experimental results compare our method with other solutions proposed in the literature and demonstrate the effectiveness of our approach toward the identification of an optimal solution to the QoS constrained Web service selection problem
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ABSTRACT: Interaction with web services enabled marketplaces would be greatly facilitated if users were given a high level service request language to express their goals in complex business domains. This could be achieved by using a planning framework which monitors the execution of planned goals against predefined standard business processes and interacts with the user to achieve goal satisfaction.International Journal on Digital Libraries 10/2003;
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ABSTRACT: This paper provides an overview of the Concurrency&Computation: Practice&Experience special issue on workflow in Grid systems. It is based on discussions at the Global Grid Forum GGF10 Workflow workshop in Berlin, March 2004 and subsequent analysis of the final papers. We describe the background from both a Grid and Global Grid Forum perspective and the distinctive features of the application requirements. We categorize different types of workflow emphasizing the important input from the distributed computing community. We discuss separately both the different workflow systems (often called (run-time) enginres) and the expression languages like BPEL. We highlight some important outstanding research issues in the conclusion.Concurrency and Computation: Practice and Experience. 01/2006; 18:1009-1019.
Conference Proceeding: Managing Energy and Server Resources in Hosting Centres.[show abstract] [hide abstract]
ABSTRACT: Internet hosting centers serve multiple service sites from a common hardware base. This paper presents the design and implementation of an architecture for resource management in a hosting center operating system, with an emphasis on as a driving resource management issue for large server clusters. The goals are to provision server resources for co-hosted services in a way that automatically adapts to offered load, improve the energy efficiency of server clusters by dynamically resizing the active server set, and respond to power supply disruptions or thermal events by degrading service in accordance with negotiated Service Level Agreements (SLAs).Our system is based on an economic approach to managing shared server resources, in which services "bid" for resources as a function of delivered performance. The system continuously monitors load and plans resource allotments by estimating the value of their effects on service performance. A greedy resource allocation algorithm adjusts resource prices to balance supply and demand, allocating resources to their most efficient use. A reconfigurable server switching infrastructure directs request traffic to the servers assigned to each service. Experimental results from a prototype confirm that the system adapts to offered load and resource availability, and can reduce server energy usage by 29% or more for a typical Web workload.01/2001