Declarative composition and peer-to-peer provisioning of dynamic Web services

Abstract

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,

Towards the Testing of Composed Web Services in 3rd Generation Networks

“…A composed web service is any web service that makes use of a set of available web services to provide a different, more complex, service. Web services composition is generating considerable interest in recent years ( [4], [5], [6]). It has a considerable potential of reducing development time and effort for new applications by reusing already available web services.…”

Model Aware Execution of Composite Web Services

“…The selection of a service is performed at runtime: a service with the highest score is chosen. In the Self-Serv environment the model of CWSs, which is specified with state-charts, is used as the execution framework [6]. To do this there are defined state coordinators for each state, and they are responsible for notifications about states completions and managing pre-and postconditions of states.…”

“…The definition of a CWS (used model/notation) Self-Serv by Benatallah et al [6,7] Service containers with membership modes: one is a query mode to query UDDI registry.…”

A Framework for the Semantic Composition of Web Services Handling User Constraints

“…In particular logicbased approaches reduce the problem of checking the existence of a composition into the satisfiability problem in a knowledge base expressed in a Description Logic [16], [18] and [11] or equivalently into the satisfiability of a formula in a theory expressed in a variant of Propositional Dynamic Logic (PDL) [4]. Some approaches have been proposed which use transitions systems as a composition framework with formalisms like Statecharts or Petri nets [13], [2], [15] and [3]. The different approaches are differentiated by the fact that they consider or not non-functional requirements for service composition based on QoS attributes [1] and [12].…”