Adaptive application-specific middleware

Abstract

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.

A systematic literature review of service choreography adaptation

“…This strategy is often used to ensure system invariants, mainly quality of service (QoS) parameters. For example, in Colman et al [3], library managers are interested in monitoring terms-of-trade to buy books from supplier services. Such terms-of-trade include cost, delivery time, supplier reputation, etc., which are QoS parameters for this application.…”

“…To avoid having the monitor as a single point of failure, Ezenwoye et al [7] state that multiple monitors could be used. In Colman et al [3], the monitor is referred to as "adaptive application-specific middleware," and is responsible for setting non-functional requirements and measuring QoS. To deal with functional requirements, monitors may track exchanged messages and try to detect unexpected content [37].…”

“…A weakness of the measurement-based approach is that retrieving the global state in distributed systems is not a trivial task: a peer state can change just after the old state is sent to the monitor, and synchronizing distributed monitors presents similar challenges. In this category, we counted five studies [3,7,16,23].…”

“…Finally, Colman [3] introduces adaptive runtime role structures that enable services to be composed and autonomously reconfigured. Dynamic contracts control interactions between services by setting and measuring non-functional requirements for these interactions.…”

“…The category aspects regarding RQ2 are: Target: Only Ezenwoy et al [7] concern functional requirements; two out of five studies concern nonfunctional requirements [16,23], and only one concerns both requirements at the same time [3].…”