The process-driven composition of Web services is emerging as a promising approach to integrate business applications within and across organizational boundaries. In this approach, individual Web services are federated into composite Web services whose business logic is expressed as a process model. The tasks of this process model are essentially invocations to functionalities offered by the underlying component services. Usually, several component services are able to execute a given task, although with different levels of pricing and quality. In this paper, we advocate that the selection of component services should be carried out during the execution of a composite service, rather than at design-time. In addition, this selection should consider multiple criteria (e.g., price, duration, reliability), and it should take into account global constraints and preferences set by the user (e.g., budget constraints). Accordingly, the paper proposes a global planning approach to optimally select component services during the execution of a composite service. Service selection is formulated as an optimization problem which can be solved using efficient linear programming methods. Experimental results show that this global planning approach outperforms approaches in which the component services are selected individually for each task in a composite service.

The development of new services through the integration of existing ones has gained a considerable momentum as a means to create and streamline business-to-business collaborations. Unfortunately, as Web services are often autonomous and heterogeneous entities, connecting and coordinating them in order to build integrated services is a delicate and time-consuming task. In this paper, we describe the design and implementation of a system through which existing Web services can be declaratively composed, and the resulting composite services can be executed following a peer-to-peer paradigm, within a dynamic environment. This system provides tools for specifying composite services through statecharts, data conversion rules, and provider selection policies. These specifications are then translated into XML documents that can be interpreted by peer-to-peer inter-connected software components, in order to provision the composite service without requiring a central authority.of Web services. In this paper, we distinguish the following key issues when composing and executing Web services:Fast composition: The "why" part of Web services composition is now widely understood [13,11]. However, the technology (i.e, the "how" part) to compose and execute Web services in appropriate time-frame, has not kept pace with the rapid growth and volatility of available opportunities. Indeed, the development of integrated Web services is still largely ad-hoc, timeconsuming and requiring a considerable effort of lowlevel programming. This approach is clearly tedious and hardly scalable because of the volatility and size of the Web. The need for fast composition and deployment of Web services, will require a high-level declarative service composition language. Scalable composition:The number of services to be integrated may be large. Consequently, approaches where the development of an integrated service requires the understanding of each of the underlying services are inappropriate. In addition, Web services may need to be composed as part of a short term partnership, and then disbanded when the partnership is no longer profitable. This form of partnership does not assume any a priori defined relationships between services. Thus, the integration of a large number of dynamic Web services, requires scalable and flexible techniques. Distributed execution:The execution of a composite service in existing techniques is usually centralised, whereas the participating services are distributed and autonomous. A centralised execution model incurs sever problems including, scalability, availability, and security problems [5]. Given the highly dynamic and distributed nature of Web services, we believe that novel techniques involving peer-to-peer execution of services will become increasingly attractive. Peer-topeer computing is gaining a considerable momentum,

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The development of user interfaces (UIs) is one of the most timeconsuming aspects in software development. In this context, the lack of proper reuse mechanisms for UIs is increasingly becoming manifest, especially as software development is more and more moving toward composite applications. In this paper we propose a framework for the integration of stand-alone modules or applications, where integration occurs at the presentation layer. Hence, the final goal is to reduce the effort required for UI development by maximizing reuse.The design of the framework is inspired by lessons learned from application integration, appropriately modified to account for the specificity of the UI integration problem. We provide an abstract component model to specify characteristics and behaviors of presentation components and propose an event-based composition model to specify the composition logic. Components and composition are described by means of a simple XML-based language, which is interpreted by a runtime middleware for the execution of the resulting composite application. A proof-ofconcept prototype allows us to show that the proposed component model can also easily be applied to existing presentation components, built with different languages and/or component technologies.

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