Different services are often required to work together to complete a task. A service composition is an aggregate of services collectively composed to automate a common task. Figure 1 shows the symbol used to represent an abstract service composition and Figure 2 illustrates a service composition from a service contract perspective that highlights which service capabilities are being invoked in a particular sequence.
Figure 1 - A generic symbol used to represent a service composition.
Figure 2 - A service composition comprised of four services. Service A is acting as the service consumer of Services B, C, and D. The arrows indicate a sequence of modeled message exchanges. Note arrow #5 representing a one-way, asynchronous data delivery from Service A to Service D.