The best way to consider both notions of service and orchestration (and process integration in general) is to think of them as independent layers, where the process layer is the calling application to the services to extract both data and behavior needed to form cohesive orchestrations. This interaction allows the architect and the developer to place certain things into certain domains. The orchestrations that define the way the services are leveraged, and the services that…well…provide service.

Orchestration is a necessity if you build a SOA, intra- or inter-organization. It’s the layer that creates business solutions from the vast array of services and information flows found in new and existing systems. Orchestration is a godlike control mechanism that’s able to put our SOA to work, as well as provide a point of control. Orchestration layers allow you to change the way your business functions, as needed, and to define or redefine any business process on-the-fly.

Read more at: InfoWorld