| Interface | Description | 
|---|---|
| IActivityHandler | Handler for executing a BPMN process activity. | 
| IInternalProcessEngineService | Services to be called from BPMN process instances
  to some super-ordinated process engine, if any. | 
| IStepHandler | Handles the transition of steps. | 
| Class | Description | 
|---|---|
| ExecuteProcessThread | Execute the next step of a process thread. | 
| ProcessServiceInvocationHandler | Invocation handler for mapping service requests to
  start events of BPMN processes. | 
| ProcessThread | Representation of a single control flow in a BPMN process instance,
  i.e. | 
| ProcessThreadValueFetcher | Value fetcher for process threads. |