Explanation/Reference:

Note E: BPM processes and sub-processes can (but are not required) themselves be exposed as SOA Services. This enables processes to be composed of SOA Services that are implemented as processes. It can be beneficial in two ways. First, it improves reuse of lower level system-centric processes (i.e. service orchestrations), and second, it offers a standard interface mechanism with which to invoke all types of business processes.
Note: BPM and SOA are often used together, as they both support a closer alignment between business and IT, and they both promote agility. BPM targets alignment and agility at the process level, while SOA applies more at the activity level. Hence, business processes and SOA Services can represent business constructs, providing a mapping between the things business does and the way IT helps get it done.
The convergence of BPM and SOA generally happens via process decomposition. That is when business processes are modeled as, (i.e. decomposed into), activities. All automated activities must be backed by some form of executable code or function call.
These functions, if they are deemed worthy, can be engineered as SOA Services following service- oriented design principles. Agility at the process level is attained by changing the process model. Agility at the service level is achieved by deploying services that are loosely coupled and independently managed.