Facilitating Semantic Adaptation of Web Services at Runtime Using a Meta-Data Layer

The migration of legacy system designs to full Service-Oriented applications raises several interesting issues, particularly surrounding co-ordination and management of the emerging system structure. Existing and emerging SOA and Web standards and technologies such as WSDL, BPEL and WS-BPEL are promoted as facilitating the design of fully-adaptive and scalable enterprise applications. However, runtime / semantic adaptation and management of software is still in its early stages. Adhering strictly to software engineering concerns such as high cohesion and low coupling results in a software architecture that promotes component (i.e. Service) reuse and lends itself to scalability. Equally, late runtime-binding, re-binding and failover systems demonstrate the flexibility in these system architectures, yet their lack of adaptability is apparent when higher-level runtime alterations would be beneficial. Current work towards this goal, such as OWL-S, still require human input at each change in order to facilitate true semantic adaptation at runtime, rendering it impractical for all but the most trivial of adaptations. This paper discusses current architectures´ shortcomings along with a proposal for a new approach within existing SOA methodologies. This approach supports source-code semantic flexibility via an intermediary Meta Data Layer (MDL), providing a layer of separation between the source code and the service.