Semantic Web services follow a life cycle, right from deployment to its invocation.

The life cycle of Semantic Web services comprises different stages like service modeling, service discovery, service definition and service delivery. The life cycle begins with modeling the web service and the service request by the provider and the consumer respectively. Web service descriptions are developed using models like OWL-S, WSMO. Service descriptions are used in the discovery stage on which discovery algorithms, matchmaking techniques are applied. Once a set of service providers are identified for a service requester, service definition takes place to select the concrete service. Finally, the concrete service is delivered to the service requester in the delivery phase.

Web service modeling is a critical aspect of the web service life cycle. It requires loads of human effort for annotating web services. Services can be modeled using two approaches viz. Code driven approach, model driven approach.

Code Driven Approach

It is assumed that the web service is already implemented, and the corresponding WSDL is generated from it. The web service can be annotated semantically by adding OWL-S specifications. Tools like Java2WSDL, WSDL2OWL-S can be used to generate abstract OWL-S specifications. The service description would later be published to the registry for discovery and invocation. This approach is referred to as the Code Driven Approach since the starting point of this process uses a web service (code).

Model Driven Approach

This approach uses the high level service descriptions to generate partial code. Service descriptions are created using ontologies and the process model is used to generate stubs for implementing the web service. The code generated is used to create the WSDL, and later published to the registry.

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