An Organisational Approach to Building Adaptive Service-oriented Systems

The relationships between the loosely coupled services of a composition can be non-deterministic and unreliable. This requires that a composite application have the ability to adaptively reconfigure itself to continuously satisfy the system requirements. Imperative composition approaches, such as BPEL, do not provide the abstractions necessary to create adaptive compositions. In this paper we introduce an organisation-oriented, application-centric service composition framework that aims to achieve adaptive application behaviour from non-deterministic and unreliable services. The responsibility for coordinating and managing service interactions resides with a coordination/management layer of the application itself. This layer involves two types of essential elements: service contracts and service organisers. The service contracts define and regulate the relationships between the services in a composition. The service organisers control the bindings between service types and individual services, and can create and revoke contracts between services within the composition in order to adaptively reconfigure the application in response to changing conditions. An adaptive service composition can be formed by connecting and configuring services through dynamically formulated contracts, under the control and management of service organisers.