The open/dynamic environment of Service-Oriented Computing requires middleware that can cope with services that are heterogeneous, and possibly unknown, unreliable or untrusted. Service-oriented middleware also needs to support both, ad-hoc and long-lived relationships between such services, and provide mechanisms for service coordination and cooperation. This needs to be achieved in a rapidly changing technical context with standards that are continually changing and evolving. This paper introduces adaptive application-specific middleware composites which are built using the ROAD framework. These composites are adaptive runtime role structures that allow services to be composed and autonomously reconfigured. In these composites, dynamic contracts control interactions between services, set non-functional requirements for those interactions, and measure the QoS of services against those requirements. These middleware composites can themselves be encapsulated as services that can be recursively composed and distributed. These composites can cope with changing requirements and performance of the services they compose. Composite roles and contracts also map naturally to business entities.

Abstract

Abstract. In a service composition, it is necessary to ensure that the behaviour of a constituent service is consistent with the requirements of the composition. In an adaptive service composition those behavioural requirements may be continually changing. This paper shows how the behavioural requirements in abstract service definitions (roles) can be dynamically and incrementally defined using constraints. These constraints are then used to generate finite state automata, which are used to check the compatibility of candidate services that have their behaviour expressed in static interface descriptions such as OWL-S.