Scheduling : Creates and manages the threads used by the runtime engine to execute workflow instances.
Commit Work Batch:
Manages the transactions used by the runtime engine to maintain consistency between the internal workflow state and external data stores.
Persistence: Handles persistence of a workflow instance at the direction of the runtime engine
Tracking: Provides the ability to instrucment workflow instances by recording tracking events. Unlike the other core services, you are permitted to register multiple tracking services with the runtime engine.