A service activity is an activity that is referenced by a service rule. At run time, the activity operates in a background requestor to perform processing and return results to the client or calling external system.
Service activities are referenced on the service rule form, typically on a form tab named Service. For example, the Service Activity field on the Service tab of the Service SOAP form identifies the second key part of an activity. The system uses information in another field of the form to determine the Applies To class of the activity.
Services operate as a BATCH requestor type and accordingly can't use methods that depend on interactive HTTP processing and human responses, such as the Show-HTML method.
On the Security tab of a service activity, select the May Start? check box to allow the service to start the activity. For maximum security, also select the Authenticate? check box unless the service runs as a guest, without authentication.
The Process Engine API activities allow services to perform BPM processing without using user forms.