In Boris's opinion, the ability to re-use services by composing them into higher-level services is one of the key benefits of SOA. After explaining the difference between hierarchical and conversational composition, the article explains different topologies, such as mediator and peer-to-peer, that can be used to compose services. Boris also describes a number of different implementation approaches, including a general purpose language, event-based composition, and use of an orchestration engine. In his opinion, the latter approach - use of an orchestration engine - yields the most benefits.
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