Abstract—The paradigmatic shift from a Web of manual interactions to a Web of programmatic interactions driven by Web services is creating unprecedented opportunities for the formation of online Business-to-Business (B2B) collaborations. In particular, the creation of value-added services by composition of existing ones is gaining a significant momentum. Since many available Web services provide overlapping or identical functionality, albeit with different Quality of Service (QoS), a choice needs to be made to determine which services are to participate in a given composite service. This paper presents a middleware platform which addresses the issue of selecting Web services for the purpose of their composition in a way that maximizes user satisfaction expressed as utility functions over QoS attributes, while satisfying the constraints set by the user and by the structure of the composite service. Two selection approaches are described and compared: one based on local (task-level) selection of services and the other based on global allocation of tasks to services using integer programming. Index Terms—Web services, quality of service, service composition, integer programming. æ 1

This papers presents XL, a new platform for Web services. We have designed XL with three main goals in mind: (a) increase application developers productivity via high-level programming constructs for Web Services routine programming patterns, (b) achieve high scalability, security, and availability for Web services and (c) compliance with all W3C standards (e.g., XML, SOAP, WSDL) such that XL Web services can interact with any other Web services written in, say, Java or C#. We hope to achieve these objectives by providing the new XL programming model based on a simple core programming "algebra" that extends Milner's PI-calculus [21]. To optimize XL programs, we employ techniques from the design of database systems, compiler construction, and data flow machines, as well as techniques specially designed for Web Services. A demo of the platform has been shown at [14].

The run-time binding of web services has been recently put forward in order to support rapid and dynamic web service compositions. With the growing number of alternative web services that provide the same functionality but differ in quality parameters, the service composition becomes a decision problem on which component services should be selected such that user’s end-to-end QoS requirements (e.g. availability, response time) and preferences (e.g. price) are satisfied. Although very efficient, local selection strategy fails short in handling global QoS requirements. Solutions based on global optimization, on the other hand, can handle global constraints, but their poor performance renders them inappropriate for applications with dynamic and realtime requirements. In this paper we address this problem and propose a solution that combines global optimization with local selection techniques to benefit from the advantages of both worlds. The proposed solution consists of two steps: first, we use mixed integer programming (MIP) to find the optimal decomposition of global QoS constraints into local constraints. Second, we use distributed local selection to find the best web services that satisfy these local constraints. The results of experimental evaluation indicate that our approach significantly outperforms existing solutions in terms of computation time while achieving close-tooptimal results.

The functionality of applications is increasingly being made available by services. General concepts and standards like SOAP, WSDL, and UDDI support the discovery and invocation of single web services. State–of–the– art process management is conceptually based on a centralized process manager. The resources of this coordinator limit the number of concurrent process executions, especially since the coordinator has to persistently store each state change for recovery purposes. In this paper, we overcome this limitation by executing processes in a peer-topeer way exploiting all nodes of the system. By distributing the execution and navigation costs, we can achieve a higher degree of scalability allowing for a much larger throughput of processes compared to centralized solutions. This papers describes our prototype system OSIRIS, which implements such a true peer–to–peer process execution. We further present very promising results verifying the advantages over centralized process management in terms of scalability. 1.

Software development nowadays involves several levels of abstraction: starting from the programming of single objects, to their combination into components, to their publication as services and the overall architecture linking elements at each level. As a result, software engineering is dealing with a wider range of artifacts and concepts (i.e., in the context of this paper: services and business processes) than ever before. In this paper we explore the importance of having an adequate engine for executing business processes written as compositions of Web services. The paper shows that, independently of the composition language used, the overall scalability of the system is determined by how the run time engine treats the process execution. This is particularly relevant at the service level because publishing a process through a Web service interface makes it accessible to an unpredictable and potentially very large number of clients. As a consequence, the process developer is confronted with the difficult question of resource provisioning. Determining the optimal configuration of the distributed engine that runs the process becomes sensitive

An increasing amount of Web services are being implemented using process management tools and languages (BPML, BPEL, etc.). The main advantage of processes is that designers can express complex business conversations at a high level of abstraction, even reusing standardized business protocols. The downside is that the infrastructure behind the Web service becomes more complex. This is particularly critical for Web services that may be subjected to high variability in demand and suffer from unpredictable peaks of heavy load. In this paper we present a flexible architecture for process execution that has been designed to support autonomic scalability. The system runs on a cluster of computers and reacts to workload variations by altering its configuration in order to optimally use the available resources. Such changes happen automatically and without any human intervention. This feature completely removes the need for the manual monitoring and reconfiguration of the system, which in practice is a difficult and time-consuming operation. In the paper we describe the architecture of the system and present an extensive performance evaluation of its autonomic capabilities. 1

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Increasingly more business models build on mechanisms for online interaction. Web Services and more recently, web service business workflows and service orchestrations provide essential tools for staging successful networked business to business (B2B) or business to customer (B2C) transactions. One of the most important online interaction quality metric is perceived response time. The ability to sustain a high throughput and provide fast service effectively means more business and associated revenue. Down-times and slow transactions can become a strong deterrent for potential customers. To achieve maximum performance with a finite set of resources, these need to be (re)allocated preferably for each new instance of a workflow execution. It is often hard for human system operators to perform such allocations appropriately to achieve maximum utilization and response times. An ability to automatically monitor and optimize response performance becomes more important than ever. In this paper we propose a solution for optimizing (web service) business workflow response times through dynamic resource allocation. On-the-fly monitoring is combined with a novel workflow modeling algorithm that discovers critical execution paths and builds “dynamic ” stochastic models in the associated “critical graph”. One novel contribution of this work is the ability to naturally handle parallel workflow execution paths. This is essential in applications where workflows include multiple concurrent service calls/paths that need to be “joined ” at a later point in time. We discuss the automatic deployment of on-the-fly monitoring mechanisms within the resource management framework. We implement, deploy and experiment with a proof of concept within a generalized web services business process (BPEL4WS/SOAP) framework. In the experimental setup we explore and show the natural adaptation to changing workflow conditions and appropriate automatic re-allocation of resources to reduce execution times.

This paper discusses a combinatorial problem about the selection of candidates for Web service compositions. The problem occurs if we assume that a discovery process has identified several candidates for each task of a composition and if the selection must consider multiple criteria. We anticipate to use quality-of-service (QoS) categories as selection criteria and thus the problem is about optimising the QoS of compositions at their planning-phase. This paper will explain this problem and propose different heuristics as possible solutions. Based on a software simulation a performance evaluation of these heuristics is given. 1

Abstract—As the amount of data generated by today’s pervasive environments increases exponentially, there is a stronger need to decipher the important information that is hidden among it. By using complex event processing, we can obtain the information that really matters to our organization and use it to improve our processes. However, even when this information is retrieved, business processes remain static and cannot be changed dynamically to adapt to the actual scenario, diminishing the advantages that can be achieved. In this paper we present CEVICHE, a framework that combines the strengths of complex event processing and dynamic business process adaptation, which allows to respond to the needs of today’s rapidly changing environments. We use a simple car rental scenario to show how CEVICHE could be used to maintain the quality of service of a business process by adapting it according to the situation. Keywords-Complex Event Processing; BPEL; process adaptation; QoS