To enhance the correctness of the composition of services, we propose a graph-based composition method that explicitly specifies and uses the functional semantics of Web services. Actions, which represent what services actually do, are identified to specify the functional semantics of services. Dependencies among services are organized and stored as an AND/OR graph, on which composition is performed. Rules are devised to map a service into an appropriate action and to identify the combined action of a composite service. The experimental results show the superiority of the proposed method in terms of the correctness of service composition.

A mobile mashup should be able to compose the component services in accordance with a user's context. We propose a context-aware mashup method for smart mobile devices. For this purpose, a novel user request model is presented and the conventional service description model is extended. We propose a context ontology which can efficiently manage contextual information in a mobile environment. Furthermore, the proposed method undergoes three computations -functional, I/O connectable and contextual matching. In particular, the contextual matching technique utilizes two types of contextual information that are proposed in this paper, implicit and explicit contexts. In order to evaluate the accuracy of the proposed method, a test registry based on real world Web APIs was built. Experimental results show an overall improvement of 26.7% in precision compared with the case where contextual information was not utilized.