The service-oriented architecture (SOA) is an emerging software engineering paradigm for developing distributed enterprise applications. In this paradigm, Web services are encapsulated and published as black-box components accessible to service consumers following the principles of component-based design. This however restricts the flexibility and adaptability of Web services to react to changing requirements, which are commonplace today, especially in the emerging smart Internet and smart interactions domain. In this chapter, we propose a grey-box approach to compose and evolve Web services to increase their flexibility and adaptability. By exposing the services' internal state changes at runtime as events, our approach allows services involved in service compositions to share and consume events from partner services, and make use of these events to evolve and adapt their behavior. This approach is illustrated in two case studies.
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